Light screen velocity measuring method with unique advantages has been widely used in the velocity measurement of various moving bodies.For large air resistance and friction force which the big moving bodies are subje...Light screen velocity measuring method with unique advantages has been widely used in the velocity measurement of various moving bodies.For large air resistance and friction force which the big moving bodies are subjected to during the light screen velocity measuring,the principle of velocity correction was proposed and a velocity correction equation was derived.A light screen velocity measuring method was used to measure the velocity of big moving bodies which have complex velocity attenuation,and the better results were gained in practical tests.The measuring uncertainty after the velocity correction was calculated.展开更多
Erosive burning is a common burning phenomenon of the gunpowder with inner holes.The actual combustion law of the gunpowder with inner holes can be changed by erosive burning.Pressure difference between the inner and ...Erosive burning is a common burning phenomenon of the gunpowder with inner holes.The actual combustion law of the gunpowder with inner holes can be changed by erosive burning.Pressure difference between the inner and the outer of hole caused by loading density variation of the propellant charge makes erosive burning occur at inner holes during in-bore burning.The effect of erosive burning on burning speed of the propellant is studied by using the effects of flow rate,heat transfer and erosion of the combustion gas in inner holes on burning rate.The mathematic model of erosive burning of the propellant is established.The effects of the factors such as loading density,inner hole size and grain length on erosive burning and interior ballistic performance are analyzed.The method to improve the bore pressure for small charge mass and small firing range by erosive burning is proposed.展开更多
探究城市洪灾韧性与生态服务价值之间耦合协调关系,对城市防洪与生态文明建设具有重要意义。研究以吉林省松花江流域为例,基于“压力-状态-响应”模型(Pressure-State-Response,PSR)结合客观权重赋权法(Criteria Importance Though Inte...探究城市洪灾韧性与生态服务价值之间耦合协调关系,对城市防洪与生态文明建设具有重要意义。研究以吉林省松花江流域为例,基于“压力-状态-响应”模型(Pressure-State-Response,PSR)结合客观权重赋权法(Criteria Importance Though Intercrieria Correlation,CRITIC)-熵权法组合权重计算吉林省松花江流域城市洪灾韧性并探究其时空分布;采用生态系统服务和权衡综合评估(Integrated Valuation of Ecosystem Services and Trade-offs,InVEST)模型分析生态系统服务中水土保持量与水源涵养量,并在县区尺度上对其进行冷热点分析及变化趋势分析;通过耦合协调度模型对城市洪灾韧性与两种生态系统服务之间的关系进行探究。研究结果显示:2010—2022年吉林省松花江流域城市洪涝韧性呈西低东高的分布特征,整体韧性由一般提升为较高水平;生态系统服务空间异质性显著,热点区域分布于植被覆盖度较高的东部与南部,冷点区域分布于西部与北部,研究区中部生态系统服务下降,南部及西北部生态系统服务提升;城市洪灾韧性与生态系统服务耦合协调性一般,其中城市洪灾韧性与水土保持量耦合协调性轻微失调,与水源涵养量初级协调,且均有继续下降的风险,生态系统服务的下降已开始制约城市洪灾韧性的提高,需及时采取措施。展开更多
文摘Light screen velocity measuring method with unique advantages has been widely used in the velocity measurement of various moving bodies.For large air resistance and friction force which the big moving bodies are subjected to during the light screen velocity measuring,the principle of velocity correction was proposed and a velocity correction equation was derived.A light screen velocity measuring method was used to measure the velocity of big moving bodies which have complex velocity attenuation,and the better results were gained in practical tests.The measuring uncertainty after the velocity correction was calculated.
文摘Erosive burning is a common burning phenomenon of the gunpowder with inner holes.The actual combustion law of the gunpowder with inner holes can be changed by erosive burning.Pressure difference between the inner and the outer of hole caused by loading density variation of the propellant charge makes erosive burning occur at inner holes during in-bore burning.The effect of erosive burning on burning speed of the propellant is studied by using the effects of flow rate,heat transfer and erosion of the combustion gas in inner holes on burning rate.The mathematic model of erosive burning of the propellant is established.The effects of the factors such as loading density,inner hole size and grain length on erosive burning and interior ballistic performance are analyzed.The method to improve the bore pressure for small charge mass and small firing range by erosive burning is proposed.
文摘探究城市洪灾韧性与生态服务价值之间耦合协调关系,对城市防洪与生态文明建设具有重要意义。研究以吉林省松花江流域为例,基于“压力-状态-响应”模型(Pressure-State-Response,PSR)结合客观权重赋权法(Criteria Importance Though Intercrieria Correlation,CRITIC)-熵权法组合权重计算吉林省松花江流域城市洪灾韧性并探究其时空分布;采用生态系统服务和权衡综合评估(Integrated Valuation of Ecosystem Services and Trade-offs,InVEST)模型分析生态系统服务中水土保持量与水源涵养量,并在县区尺度上对其进行冷热点分析及变化趋势分析;通过耦合协调度模型对城市洪灾韧性与两种生态系统服务之间的关系进行探究。研究结果显示:2010—2022年吉林省松花江流域城市洪涝韧性呈西低东高的分布特征,整体韧性由一般提升为较高水平;生态系统服务空间异质性显著,热点区域分布于植被覆盖度较高的东部与南部,冷点区域分布于西部与北部,研究区中部生态系统服务下降,南部及西北部生态系统服务提升;城市洪灾韧性与生态系统服务耦合协调性一般,其中城市洪灾韧性与水土保持量耦合协调性轻微失调,与水源涵养量初级协调,且均有继续下降的风险,生态系统服务的下降已开始制约城市洪灾韧性的提高,需及时采取措施。
