Unmanned surface vehicles(USVs)play a crucial role in various fields,including ocean climate change monitoring,ma-rine resource exploitation,and ecological environment exploration.Out of the many types of USVs,unmanne...Unmanned surface vehicles(USVs)play a crucial role in various fields,including ocean climate change monitoring,ma-rine resource exploitation,and ecological environment exploration.Out of the many types of USVs,unmanned sailboats have gained considerable attention for their ability to conduct green,large-scale ocean observations.Building on this concept,this paper proposes an unmanned sailboat propelled by parallel dual-wing sails,which is designed to meet the demands of extensive and three-dimensional marine comprehensive observation and data collection.With a focus on the parallel dual-wing sails,this study particularly investi-gates the effects of variations in the airfoil’s angle of attack and the impact of the spacing ratio between the dual sails on propulsion performance.It further analyzes the influence of one sail’s angle of attack on the performance of the other sail,as well as the flow field between the two sails.For the air navigation and underwater states,the force characteristics of the dual sail under different inflow velocities were investigated.The research findings indicate that,under certain conditions,the thrust coefficient exhibits a trend of first increasing,then decreasing,and finally increasing again with alterations in the angle of attackα.Different single-sail angles of attack have varying impacts on the opposite sail and the flow field between the dual sails.Moreover,the generated forces are positively correlated with inflow velocity in the air navigation and underwater states.The findings reveal that it is possible to reduce drag,mitigate the adverse effects of sail interaction,and thereby enhance the propulsion performance and overall navigational stability of the sailboat by applying an optimal spacing ratio design and adjusting the angle of attack and inflow velocity.展开更多
The legal framework for outer space governance,centered on the“Five Major Treaties”,is facing significant challenges.In the face of numerous variables that will shape the future order of outer space,an intrinsic dem...The legal framework for outer space governance,centered on the“Five Major Treaties”,is facing significant challenges.In the face of numerous variables that will shape the future order of outer space,an intrinsic demand for transformation has emerged within the governance of outer space.Under the leadership of the new wave of space technology revolutions and commercial innovations,outer space governance will undergo a profound transformation.New theories in space law will emerge,engage in long-term competition,and ultimately contribute to the formation of a completely new governance structure.展开更多
听觉系统各组成部分的机械损伤是爆炸后造成听力损失的主要原因,强脉冲声致听觉损害风险准则仍然存在许多争议,例如:指标选择冲量还是超压峰值,正压持续时间是否重要等。本研究基于自由场实爆条件,设计并搭建了大动物爆炸致伤平台,探究...听觉系统各组成部分的机械损伤是爆炸后造成听力损失的主要原因,强脉冲声致听觉损害风险准则仍然存在许多争议,例如:指标选择冲量还是超压峰值,正压持续时间是否重要等。本研究基于自由场实爆条件,设计并搭建了大动物爆炸致伤平台,探究了不同爆炸参数对鼓膜破裂的影响规律,并建立了基于自由场超压峰值和正压持续时间的鼓膜创伤量效关系。通过笔形压力传感器测量自由场超压,通过Friedlander公式拟合超压时程曲线,确定冲击波超压峰值和正压持续时间,并对时域中记录的波形进行归一化能量频谱分析,以确定冲击波在频域上的信号能量分布。对爆炸后的小型猪进行解剖,记录不同爆炸参数下鼓膜创伤程度。以超压峰值和正压持续时间为自变量,对实验数据进行二元逻辑回归分析,并给出鼓膜破裂风险曲线。研究发现,当自由场超压峰值低于170 kPa时,鼓膜无明显损伤;当自由场超压峰值高于237 kPa时,部分鼓膜出现不同程度的破裂和充血。距爆心越近,超压峰值越大,但鼓膜创伤的严重程度并未随之单调增加。在8.0 kg TNT当量的爆炸实验中,鼓膜破裂的严重程度随爆心距的减小呈现先提高再降低的趋势。通过对冲击波载荷特征的分析可知,距爆心越近,正压持续时间越短,高频段能量占比相对更大,小型猪鼓膜破裂的概率可能反而降低,此时仍然出现显著的听力损失和耳蜗损伤。鼓膜作为通过振动传递声信号的黏弹性薄膜结构,其动力学响应可能与载荷频率成分密切相关。除了超压峰值,冲击波波形频谱分布对鼓膜破裂程度影响显著。展开更多
为提高增塑剂的阻燃性能,以可再生资源蓖麻油合成了一种蓖麻油基含硅阻燃增塑剂(Si-ECO),并将其应用到聚氯乙烯(PVC)中。首先将蓖麻油与三甲基氯硅烷反应得到中间体(Si-CO),再与双氧水、甲酸等进行环氧化得到最终产品。采用傅里叶红外光...为提高增塑剂的阻燃性能,以可再生资源蓖麻油合成了一种蓖麻油基含硅阻燃增塑剂(Si-ECO),并将其应用到聚氯乙烯(PVC)中。首先将蓖麻油与三甲基氯硅烷反应得到中间体(Si-CO),再与双氧水、甲酸等进行环氧化得到最终产品。采用傅里叶红外光谱(FT-IR)和核磁共振氢谱(~1H NMR)对分子结构进行表征。将该蓖麻油基含硅增塑剂与PVC以及其他助剂进行共混注塑,得到不同含量Si-ECO的PVC树脂。以动态机械分析(DMA)、热重(TG)以及极限氧指数(LOI)等方法测试共混树脂的热力学性能和阻燃性能;以万能力学试验机表征力学性能。试验结果表明:随着Si-ECO阻燃增塑剂含量的增加,其热稳定性有所提高,同时残炭量也增加到4.72%;通过DMA分析可知,该蓖麻油基增塑剂Si-ECO与PVC具有良好的相容性,且能有效提高树脂的阻燃性能,体系的LOI从25.0增加到30.7,热释放速率(HRR)和总释放热(THR)分别为263.14 k W/m^2和29.5 MJ。以蓖麻油为基础合成具有阻燃功能的增塑剂具有广阔的发展前景。展开更多
基金supported from the Shandong Provincial Natural Science Foundation(No.ZR2022ME147)the National Natural Science Foundation of China(No.52088102).
文摘Unmanned surface vehicles(USVs)play a crucial role in various fields,including ocean climate change monitoring,ma-rine resource exploitation,and ecological environment exploration.Out of the many types of USVs,unmanned sailboats have gained considerable attention for their ability to conduct green,large-scale ocean observations.Building on this concept,this paper proposes an unmanned sailboat propelled by parallel dual-wing sails,which is designed to meet the demands of extensive and three-dimensional marine comprehensive observation and data collection.With a focus on the parallel dual-wing sails,this study particularly investi-gates the effects of variations in the airfoil’s angle of attack and the impact of the spacing ratio between the dual sails on propulsion performance.It further analyzes the influence of one sail’s angle of attack on the performance of the other sail,as well as the flow field between the two sails.For the air navigation and underwater states,the force characteristics of the dual sail under different inflow velocities were investigated.The research findings indicate that,under certain conditions,the thrust coefficient exhibits a trend of first increasing,then decreasing,and finally increasing again with alterations in the angle of attackα.Different single-sail angles of attack have varying impacts on the opposite sail and the flow field between the dual sails.Moreover,the generated forces are positively correlated with inflow velocity in the air navigation and underwater states.The findings reveal that it is possible to reduce drag,mitigate the adverse effects of sail interaction,and thereby enhance the propulsion performance and overall navigational stability of the sailboat by applying an optimal spacing ratio design and adjusting the angle of attack and inflow velocity.
文摘The legal framework for outer space governance,centered on the“Five Major Treaties”,is facing significant challenges.In the face of numerous variables that will shape the future order of outer space,an intrinsic demand for transformation has emerged within the governance of outer space.Under the leadership of the new wave of space technology revolutions and commercial innovations,outer space governance will undergo a profound transformation.New theories in space law will emerge,engage in long-term competition,and ultimately contribute to the formation of a completely new governance structure.
文摘听觉系统各组成部分的机械损伤是爆炸后造成听力损失的主要原因,强脉冲声致听觉损害风险准则仍然存在许多争议,例如:指标选择冲量还是超压峰值,正压持续时间是否重要等。本研究基于自由场实爆条件,设计并搭建了大动物爆炸致伤平台,探究了不同爆炸参数对鼓膜破裂的影响规律,并建立了基于自由场超压峰值和正压持续时间的鼓膜创伤量效关系。通过笔形压力传感器测量自由场超压,通过Friedlander公式拟合超压时程曲线,确定冲击波超压峰值和正压持续时间,并对时域中记录的波形进行归一化能量频谱分析,以确定冲击波在频域上的信号能量分布。对爆炸后的小型猪进行解剖,记录不同爆炸参数下鼓膜创伤程度。以超压峰值和正压持续时间为自变量,对实验数据进行二元逻辑回归分析,并给出鼓膜破裂风险曲线。研究发现,当自由场超压峰值低于170 kPa时,鼓膜无明显损伤;当自由场超压峰值高于237 kPa时,部分鼓膜出现不同程度的破裂和充血。距爆心越近,超压峰值越大,但鼓膜创伤的严重程度并未随之单调增加。在8.0 kg TNT当量的爆炸实验中,鼓膜破裂的严重程度随爆心距的减小呈现先提高再降低的趋势。通过对冲击波载荷特征的分析可知,距爆心越近,正压持续时间越短,高频段能量占比相对更大,小型猪鼓膜破裂的概率可能反而降低,此时仍然出现显著的听力损失和耳蜗损伤。鼓膜作为通过振动传递声信号的黏弹性薄膜结构,其动力学响应可能与载荷频率成分密切相关。除了超压峰值,冲击波波形频谱分布对鼓膜破裂程度影响显著。
文摘为提高增塑剂的阻燃性能,以可再生资源蓖麻油合成了一种蓖麻油基含硅阻燃增塑剂(Si-ECO),并将其应用到聚氯乙烯(PVC)中。首先将蓖麻油与三甲基氯硅烷反应得到中间体(Si-CO),再与双氧水、甲酸等进行环氧化得到最终产品。采用傅里叶红外光谱(FT-IR)和核磁共振氢谱(~1H NMR)对分子结构进行表征。将该蓖麻油基含硅增塑剂与PVC以及其他助剂进行共混注塑,得到不同含量Si-ECO的PVC树脂。以动态机械分析(DMA)、热重(TG)以及极限氧指数(LOI)等方法测试共混树脂的热力学性能和阻燃性能;以万能力学试验机表征力学性能。试验结果表明:随着Si-ECO阻燃增塑剂含量的增加,其热稳定性有所提高,同时残炭量也增加到4.72%;通过DMA分析可知,该蓖麻油基增塑剂Si-ECO与PVC具有良好的相容性,且能有效提高树脂的阻燃性能,体系的LOI从25.0增加到30.7,热释放速率(HRR)和总释放热(THR)分别为263.14 k W/m^2和29.5 MJ。以蓖麻油为基础合成具有阻燃功能的增塑剂具有广阔的发展前景。
