Composite solid propellants(CSPs) have widely been used as main energy source for propelling the rockets in both space and military applications. Internal ballistic parameters of rockets like characteristic exhaust ve...Composite solid propellants(CSPs) have widely been used as main energy source for propelling the rockets in both space and military applications. Internal ballistic parameters of rockets like characteristic exhaust velocity, specific impulse, thrust, burning rate etc., are measured to assess and control the performance of rocket motors. The burn rate of solid propellants has been considered as most vital parameter for design of solid rocket motors to meet specific mission requirements. The burning rate of solid propellants can be tailored by using different constituents, extent of oxidizer loading and its particle size and more commonly by incorporating suitable combustion catalysts. Various metal oxides(MOs),complexes, metal powders and metal alloys have shown positive catalytic behaviour during the combustion of CSPs. These are usually solid-state catalysts that play multiple roles in combustion of CSPs such as reduction in activation energy, enhancement of rate of reaction, modification of sequences in reaction-phase, influence on condensed-phase combustion and participation in combustion process in gas-phase reactions. The application of nanoscale catalysts in CSPs has increased considerably in recent past due to their superior catalytic properties as compared to their bulk-sized counterparts. A large surface-to-volume ratio and quantum size effect of nanocatalysts are considered to be plausible reasons for improving the combustion characteristics of propellants. Several efforts have been made to produce nanoscale combustion catalysts for advanced propellant formulations to improve their energetics. The work done so far is largely scattered. In this review, an effort has been made to introduce various combustion catalysts having at least a metallic entity. Recent developments of nanoscale combustion catalysts with their specific merits are discussed. The combustion chemistry of a typical CSP is briefly discussed for providing a better understanding on role of combustion catalysts in burning rate enhancement. 展开更多
目的:分析皮下注射低分子肝素钙对烧伤植皮后深静脉血栓、创面愈合及感染率的影响。方法:将我院2015年2月-2017年2月收治的200例烧伤需要植皮的患者随机分为观察组(基础治疗基础上加用皮下注射低分子肝素钙治疗,术前1 d~术后3 d 2 800 I...目的:分析皮下注射低分子肝素钙对烧伤植皮后深静脉血栓、创面愈合及感染率的影响。方法:将我院2015年2月-2017年2月收治的200例烧伤需要植皮的患者随机分为观察组(基础治疗基础上加用皮下注射低分子肝素钙治疗,术前1 d~术后3 d 2 800 IU/d,术后4~7 d 4 800 IU/d)和对照组(仅采用红外线理疗仪照射、热敷、肌肉按摩等基础治疗),每组100例。观察两组患者烧伤植皮后3、7、11 d D-二聚体、血小板变化,创面愈合情况,以及深静脉血栓、感染等并发症发生情况。结果:观察组术后第3、7、11天的血浆D-二聚体浓度、血小板数量均明显低于对照组(P<0.05),观察组DVT发生率为0,明显低于对照组的6.0%(6例,P<0.05);观察组术后创面愈合时间与对照组比较差异无显著性,而观察组感染率为2.0%,明显低于对照组的10.0%(P<0.05)。结论:皮下注射低分子肝素钙,可以有效预防烧伤植皮患者深静脉血栓形成,并且降低感染率。展开更多
Technologies for reducing corn leaf burn caused by foliar spray of urea-ammonium nitrate (UAN) during the early growing season are limited. A field experiment was carried out to evaluate the effects of humic acid on c...Technologies for reducing corn leaf burn caused by foliar spray of urea-ammonium nitrate (UAN) during the early growing season are limited. A field experiment was carried out to evaluate the effects of humic acid on corn leaf burn caused by foliar spray of undiluted UAN solution on corn canopy at Jackson, TN in 2018. Thirteen treatments of the mixtures of UAN and humic acid were evaluated at V6 of corn with different UAN application rates and different UAN/humic acid ratios. Leaf burn during 1 2, 3, 4, 5, 6, 7, and 14 days after UAN foliar spray significantly differed between with or without humic acid addition. The addition of humic acid to UAN significantly reduced leaf burn at each UAN application rate (15, 25, and 35 gal/acre). The reduction of leaf burn was enhanced as the humic acid/UAN ratio went up from 10% to 30%. Leaf burn due to foliar application of UAN became severer with higher UAN rates. The linear regression of leaf burn 14 days after application with humic acid/UAN ratio was highly significant and negative. However, the linear regression of leaf burn 14 days after application with the UAN application rate was highly significant and positive. In conclusion, adding humic acid to foliar-applied UAN is beneficial for reducing corn leaf burn during the early growing season.展开更多
In the present investigation an effort has been made to understand the thermal decomposition and burn rate characteristics of AP as oxidizer and PVC and HTPB as fuel binder in composite solid propellant. The burning r...In the present investigation an effort has been made to understand the thermal decomposition and burn rate characteristics of AP as oxidizer and PVC and HTPB as fuel binder in composite solid propellant. The burning rate study has been carried out at ambient and different pressures of 2.068 Mpa, 4.760 Mpa,6.895 Mpa. The mechanism of thermal decomposition of each composition have also been determined by NETZSCH simultaneous thermal analyser, comprising differential scanning calorimeter(DSC) and thermo-gravimetric analyser(TGA). An effort has been made to study the burn rate and decomposition of fuel binder and oxidizer in presence of Fe_2O_3 and also their overall impact on combustion of propellant.展开更多
文摘Composite solid propellants(CSPs) have widely been used as main energy source for propelling the rockets in both space and military applications. Internal ballistic parameters of rockets like characteristic exhaust velocity, specific impulse, thrust, burning rate etc., are measured to assess and control the performance of rocket motors. The burn rate of solid propellants has been considered as most vital parameter for design of solid rocket motors to meet specific mission requirements. The burning rate of solid propellants can be tailored by using different constituents, extent of oxidizer loading and its particle size and more commonly by incorporating suitable combustion catalysts. Various metal oxides(MOs),complexes, metal powders and metal alloys have shown positive catalytic behaviour during the combustion of CSPs. These are usually solid-state catalysts that play multiple roles in combustion of CSPs such as reduction in activation energy, enhancement of rate of reaction, modification of sequences in reaction-phase, influence on condensed-phase combustion and participation in combustion process in gas-phase reactions. The application of nanoscale catalysts in CSPs has increased considerably in recent past due to their superior catalytic properties as compared to their bulk-sized counterparts. A large surface-to-volume ratio and quantum size effect of nanocatalysts are considered to be plausible reasons for improving the combustion characteristics of propellants. Several efforts have been made to produce nanoscale combustion catalysts for advanced propellant formulations to improve their energetics. The work done so far is largely scattered. In this review, an effort has been made to introduce various combustion catalysts having at least a metallic entity. Recent developments of nanoscale combustion catalysts with their specific merits are discussed. The combustion chemistry of a typical CSP is briefly discussed for providing a better understanding on role of combustion catalysts in burning rate enhancement.
文摘目的:分析皮下注射低分子肝素钙对烧伤植皮后深静脉血栓、创面愈合及感染率的影响。方法:将我院2015年2月-2017年2月收治的200例烧伤需要植皮的患者随机分为观察组(基础治疗基础上加用皮下注射低分子肝素钙治疗,术前1 d~术后3 d 2 800 IU/d,术后4~7 d 4 800 IU/d)和对照组(仅采用红外线理疗仪照射、热敷、肌肉按摩等基础治疗),每组100例。观察两组患者烧伤植皮后3、7、11 d D-二聚体、血小板变化,创面愈合情况,以及深静脉血栓、感染等并发症发生情况。结果:观察组术后第3、7、11天的血浆D-二聚体浓度、血小板数量均明显低于对照组(P<0.05),观察组DVT发生率为0,明显低于对照组的6.0%(6例,P<0.05);观察组术后创面愈合时间与对照组比较差异无显著性,而观察组感染率为2.0%,明显低于对照组的10.0%(P<0.05)。结论:皮下注射低分子肝素钙,可以有效预防烧伤植皮患者深静脉血栓形成,并且降低感染率。
文摘Technologies for reducing corn leaf burn caused by foliar spray of urea-ammonium nitrate (UAN) during the early growing season are limited. A field experiment was carried out to evaluate the effects of humic acid on corn leaf burn caused by foliar spray of undiluted UAN solution on corn canopy at Jackson, TN in 2018. Thirteen treatments of the mixtures of UAN and humic acid were evaluated at V6 of corn with different UAN application rates and different UAN/humic acid ratios. Leaf burn during 1 2, 3, 4, 5, 6, 7, and 14 days after UAN foliar spray significantly differed between with or without humic acid addition. The addition of humic acid to UAN significantly reduced leaf burn at each UAN application rate (15, 25, and 35 gal/acre). The reduction of leaf burn was enhanced as the humic acid/UAN ratio went up from 10% to 30%. Leaf burn due to foliar application of UAN became severer with higher UAN rates. The linear regression of leaf burn 14 days after application with humic acid/UAN ratio was highly significant and negative. However, the linear regression of leaf burn 14 days after application with the UAN application rate was highly significant and positive. In conclusion, adding humic acid to foliar-applied UAN is beneficial for reducing corn leaf burn during the early growing season.
文摘In the present investigation an effort has been made to understand the thermal decomposition and burn rate characteristics of AP as oxidizer and PVC and HTPB as fuel binder in composite solid propellant. The burning rate study has been carried out at ambient and different pressures of 2.068 Mpa, 4.760 Mpa,6.895 Mpa. The mechanism of thermal decomposition of each composition have also been determined by NETZSCH simultaneous thermal analyser, comprising differential scanning calorimeter(DSC) and thermo-gravimetric analyser(TGA). An effort has been made to study the burn rate and decomposition of fuel binder and oxidizer in presence of Fe_2O_3 and also their overall impact on combustion of propellant.
