Additive Manufacturing(AM)can provide customized parts that conventional techniques fail to deliver.One important parameter in AM is the quality of the parts,as a result of the material extrusion 3D printing(3D-P)proc...Additive Manufacturing(AM)can provide customized parts that conventional techniques fail to deliver.One important parameter in AM is the quality of the parts,as a result of the material extrusion 3D printing(3D-P)procedure.This can be very important in defense-related applications,where optimum performance needs to be guaranteed.The quality of the Polyetherimide 3D-P specimens was examined by considering six control parameters,namely,infill percentage,layer height,deposition angle,travel speed,nozzle,and bed temperature.The quality indicators were the root mean square(Rq)and average(Ra)roughness,porosity,and the actual to nominal dimensional deviation.The examination was performed with optical profilometry,optical microscopy,and micro-computed tomography scanning.The Taguchi design of experiments was applied,with twenty-five runs,five levels for each control parameter,on five replicas.Two additional confirmation runs were conducted,to ensure reliability.Prediction equations were constructed to express the quality indicators in terms of the control parameters.Three modeling approaches were applied to the experimental data,to compare their efficiency,i.e.,Linear Regression Model(LRM),Reduced Quadratic Regression Model,and Quadratic Regression Model(QRM).QRM was the most accurate one,still the differences were not high even considering the simpler LRM model.展开更多
为了解决石化行业节能减排技术评估体系构建尚不完善的问题,聚焦石化行业节能减排技术,从技术性能、经济效益和环境保护3方面构建评价指标体系,通过CRITIC(criteria importance though intercrieria correlation)-云模型进行评价。结果...为了解决石化行业节能减排技术评估体系构建尚不完善的问题,聚焦石化行业节能减排技术,从技术性能、经济效益和环境保护3方面构建评价指标体系,通过CRITIC(criteria importance though intercrieria correlation)-云模型进行评价。结果表明:石化行业75%的节能减排技术综合评分在0.6以上,其中变频器调速节能技术、蒸汽系统运行优化与节能技术、大型高参数板壳式换热技术是标杆技术;石化行业节能减排技术在成熟度、适用性、减排成本以及减排潜力上的表现存在显著差异,其中多能互补型直流微电网及抽油机节能群控系统技术与多孔表面高通量管高效换热技术在经济效益和环境效益方面亟待改进;云模型评价显示,石化行业节能减排技术整体处于“可接受级”水平,并逐步向“可宣称级”水平迈进。研究结果从技术评价视角为石化行业锚定发展节能减排技术提供了评价依据,有助于助推“双碳”目标的达成。展开更多
锂离子电池储能电站火灾事故频繁发生且损失严重,对锂离子电池储能电站火灾风险开展研究可有效预防火灾的发生。首先根据物理-事理-人理(WSR)理论,构建锂电池特性、消防设施、安全管理和人员因素4个一级指标、12个二级指标和32个三级指...锂离子电池储能电站火灾事故频繁发生且损失严重,对锂离子电池储能电站火灾风险开展研究可有效预防火灾的发生。首先根据物理-事理-人理(WSR)理论,构建锂电池特性、消防设施、安全管理和人员因素4个一级指标、12个二级指标和32个三级指标的锂离子电池储能电站火灾风险评价指标体系;然后运用序关系分析(G1)法确定各评价指标的主观权重,采用CRITIC法(Criteria Importance Though Intercriteria Correlation,CRITIC)确定客观权重,基于拉格朗日乘法优化后的最小信息熵原理确定组合权重,并结合云模型理论建立锂离子电池储能电站火灾风险评价模型。以某磷酸铁锂储能电站为例开展火灾风险等级评价,结果表明:储能电站火灾风险综合云特征值为(71.3104,1.2142,0.2568),火灾风险等级处于“中风险”,在运行环境和防火设计等方面存在较严重的问题并亟需改进。评价结果与实际火灾风险等级相符,实例证明锂离子电池储能电站火灾风险评价模型能够较准确地反映储能电站火灾风险情况,为锂离子电池储能电站火灾预防与风险管控提供参考。展开更多
基于次加载面的砂黏统一本构模型(clay and sand model with subloading surface,简称CASM-S)适用于描述砂土和超固结黏土的力学行为,然而该模型仍沿用线性临界状态描述砂土的应力−孔隙比关系。考虑高应力状态下砂土的压缩特性及其临界...基于次加载面的砂黏统一本构模型(clay and sand model with subloading surface,简称CASM-S)适用于描述砂土和超固结黏土的力学行为,然而该模型仍沿用线性临界状态描述砂土的应力−孔隙比关系。考虑高应力状态下砂土的压缩特性及其临界状态线在e-lnp平面内的非线性,在CASM-S中引入了描述砂土非线性临界状态线和参考固结线(reference compression curve,简称RCC)的幂函数形式;通过引入参数ξ和λ_(r),修正了CASM-S的屈服面与次加载面函数以描述砂土剪切特性,并利用参考固结线在e-(p/p_(a))^(ξ)(其中e为临界状态下的孔隙比,p为正应力,pa为标准大气压)平面内的线性关系给出了先期固结压力p_(c)0的求解方法。新建本构模型的11个参数均可通过常规土工试验或经验方法确定。基于修正CASM-S的预测结果,对比分析了4种砂土的三轴排水和不排水剪切试验结果,证实了该模型能够有效考虑非线性临界状态线的影响,并能够精确描述饱和砂土在不同孔隙比和围压下的三轴剪切特性。展开更多
文摘Additive Manufacturing(AM)can provide customized parts that conventional techniques fail to deliver.One important parameter in AM is the quality of the parts,as a result of the material extrusion 3D printing(3D-P)procedure.This can be very important in defense-related applications,where optimum performance needs to be guaranteed.The quality of the Polyetherimide 3D-P specimens was examined by considering six control parameters,namely,infill percentage,layer height,deposition angle,travel speed,nozzle,and bed temperature.The quality indicators were the root mean square(Rq)and average(Ra)roughness,porosity,and the actual to nominal dimensional deviation.The examination was performed with optical profilometry,optical microscopy,and micro-computed tomography scanning.The Taguchi design of experiments was applied,with twenty-five runs,five levels for each control parameter,on five replicas.Two additional confirmation runs were conducted,to ensure reliability.Prediction equations were constructed to express the quality indicators in terms of the control parameters.Three modeling approaches were applied to the experimental data,to compare their efficiency,i.e.,Linear Regression Model(LRM),Reduced Quadratic Regression Model,and Quadratic Regression Model(QRM).QRM was the most accurate one,still the differences were not high even considering the simpler LRM model.
文摘为了解决石化行业节能减排技术评估体系构建尚不完善的问题,聚焦石化行业节能减排技术,从技术性能、经济效益和环境保护3方面构建评价指标体系,通过CRITIC(criteria importance though intercrieria correlation)-云模型进行评价。结果表明:石化行业75%的节能减排技术综合评分在0.6以上,其中变频器调速节能技术、蒸汽系统运行优化与节能技术、大型高参数板壳式换热技术是标杆技术;石化行业节能减排技术在成熟度、适用性、减排成本以及减排潜力上的表现存在显著差异,其中多能互补型直流微电网及抽油机节能群控系统技术与多孔表面高通量管高效换热技术在经济效益和环境效益方面亟待改进;云模型评价显示,石化行业节能减排技术整体处于“可接受级”水平,并逐步向“可宣称级”水平迈进。研究结果从技术评价视角为石化行业锚定发展节能减排技术提供了评价依据,有助于助推“双碳”目标的达成。
文摘锂离子电池储能电站火灾事故频繁发生且损失严重,对锂离子电池储能电站火灾风险开展研究可有效预防火灾的发生。首先根据物理-事理-人理(WSR)理论,构建锂电池特性、消防设施、安全管理和人员因素4个一级指标、12个二级指标和32个三级指标的锂离子电池储能电站火灾风险评价指标体系;然后运用序关系分析(G1)法确定各评价指标的主观权重,采用CRITIC法(Criteria Importance Though Intercriteria Correlation,CRITIC)确定客观权重,基于拉格朗日乘法优化后的最小信息熵原理确定组合权重,并结合云模型理论建立锂离子电池储能电站火灾风险评价模型。以某磷酸铁锂储能电站为例开展火灾风险等级评价,结果表明:储能电站火灾风险综合云特征值为(71.3104,1.2142,0.2568),火灾风险等级处于“中风险”,在运行环境和防火设计等方面存在较严重的问题并亟需改进。评价结果与实际火灾风险等级相符,实例证明锂离子电池储能电站火灾风险评价模型能够较准确地反映储能电站火灾风险情况,为锂离子电池储能电站火灾预防与风险管控提供参考。
文摘基于次加载面的砂黏统一本构模型(clay and sand model with subloading surface,简称CASM-S)适用于描述砂土和超固结黏土的力学行为,然而该模型仍沿用线性临界状态描述砂土的应力−孔隙比关系。考虑高应力状态下砂土的压缩特性及其临界状态线在e-lnp平面内的非线性,在CASM-S中引入了描述砂土非线性临界状态线和参考固结线(reference compression curve,简称RCC)的幂函数形式;通过引入参数ξ和λ_(r),修正了CASM-S的屈服面与次加载面函数以描述砂土剪切特性,并利用参考固结线在e-(p/p_(a))^(ξ)(其中e为临界状态下的孔隙比,p为正应力,pa为标准大气压)平面内的线性关系给出了先期固结压力p_(c)0的求解方法。新建本构模型的11个参数均可通过常规土工试验或经验方法确定。基于修正CASM-S的预测结果,对比分析了4种砂土的三轴排水和不排水剪切试验结果,证实了该模型能够有效考虑非线性临界状态线的影响,并能够精确描述饱和砂土在不同孔隙比和围压下的三轴剪切特性。
