宽带激光熔覆送粉喷嘴的结构设计与粉末流场研究

设计一种新型的送粉喷嘴结构,适用于宽带激光熔覆和增材制造。该结构使用多通道出口有效降低粉末流在扫描方向的发散角,通过添加内部整流圆柱调整粉末流在垂直扫描方向上的浓度分布。采用离散相模型,研究该喷嘴结构输出的粉末流场。优化分流圆柱的尺寸,使该送粉喷嘴能够输出浓度分布均匀的宽带粉末流,并沉积出厚度均匀的宽带涂层。     

气相色谱法测定奶粉中香兰素的含量

建立了氢火焰离子化检测器一气相色谱法(FID-GC)检测奶粉中香兰素含量的方法.考察了不同萃取剂对样品预处理的影响,同时对色谱分离条件如毛细管柱极性、柱温及载气流速等条件进行了优化,目标峰获得良好分离.标准曲线方程为y=8539099x-2189,R=0.9995,方法检出限0.003mg.g-1;加标回收率介于93.8%～99.4%之间.RSD=2.5%(n=5).所建立的方法用于实际样品测定获得满意结果.     

消解条件对微波消解-火焰原子吸收法测定奶粉铅的影响

研究了酸度、消解时间、消解功率对微波消解-火焰原子吸收光谱法测定奶粉铅含量的影响。结果表明:酸度对测定结果有较大影响,p H 2.0时铅元素的测定值最大;消解时间在8~10 min内奶粉消解完全;消解功率越高,则消解越彻底,而分步调高功率消解效果同样良好。     

漂白粉的火灾危险性研究

通过分析漂白粉纯样、受潮样品和含有氧化铁的样品受热条件下发生的热解过程,发现水分和氧化铁的存在会促进漂白粉的受热分解.通过自行设计的漂白粉遇水受潮自热实验装置模拟漂白粉在长时间暴露于潮湿空气中的体系热聚集效应.发现在潮湿空气下,漂白能够聚集热量,导致内部温度的升高.从热解动力学的角度证实了氧化铁和水的存在降低了漂白粉分解时的活化能而导致反应速率增大.     

石粉CFG桩在路基工程中应用分析

文章分析石粉CFG桩在公路中应用,阐述了石粉CFG桩复合地基设计,介绍石粉CFG桩设计长度、桩径、桩间距、桩身强度、桩身材料、褥垫层及布桩形式、单桩及复合地基承载力,通过施工及质量检测达到了设计标准,为石粉CFG桩施工提供一定参考。     

我国乳品企业社会责任缺失的原因及对策——以“皮革奶”为例

在安全事故频发的我国乳制品行业,消费者明显已对我国乳业信心不足。针对这一特殊行业,从消费者的视角界定了企业社会责任的主要内容,并分析了乳品企业社会责任缺失的原因,最后提出了驱动乳品企业承担社会责任的对策：宏观上依靠完善的法律,有效的执法及乳品企业的诚信体系建设;中观上依靠行业协会有效的引导与规范;微观上依靠广大的消费者及大众媒体对乳品企业进行监督。     

高温萤石粉的气力输送

通过工程实践,证实了稀相正压气力输送系统用于小规模高温萤石粉输送的可行性,推荐了料气混合比、输送气流流速等几个重要的设计参数.     

竹屑成分测定及其精度分析

作者率领13组学生对竹青、15组学生对竹黄的5个项目的化学成分进行测定。采用区间估计、假设检验等数理统计方法对实验数据进行了分析,得到竹青竹黄的五项成分无明显区别,基本成分为水分11.13%,灰分1.04%,苯醇抽出物6.05%,纤维素41.27%,木质素23.00%。最后对28组实验数据的精度进行了分析,由此给出学生成绩排序的一种方法。     

Preparation and Dynamic Tensile Behavior of C200 Green Reactive Powder Concrete

A new type of green reactive powder concrete (GRPC) with compressive strength of 200 MPa is prepared by utilizing composite mineral admixtures, natural fine aggregates, and short and fine steel fibers. The quasi-static mechanical properties (mechanical strength, toughness, fracture energy and interfacial bonding strength) of GRPC specimens, cured in three different types of regimes, are investigated. The experimental results show that the mechanical properties of the C200 GRPC made with the powder binders that is composed of 40% of Portland cement, 25% of ultra fine slag, 25% of ultra fine fly ash and 10% of silica fume are better than the others'. The corresponding compressive strength, flexural strength and fracture energy are more than 200 MPa, and 30 000 J/ m2 respectively. The dynamic tensile behavior of the C200 GRPC is also investigated through the split Hopkinson pressure bar (SHPB) according to the spalling phenomenon. The dynamic testing results demonstrate that strain rate has an important effect on the dynamic tensile behavior of GRPC. With the increase of strain rate, its peak stress and relevant strain increase. The GRPC exhibits an excellent strain ratio stiffening effect under the dynamic tensile load with high strain ratio, resulting in a significant change of the fracture pattern.     

Safety control for powder compaction of initiating explosive device

1 Introduction The initiating explosive device is a component or device filled with powder, which releases abundant energy in burning or exploding upon a small environmental strike and is applied to igniting, detonating or special application device. It is widely used in aerospace, motor, mining or weapon systems, etc. The powder is the energy source of initiating explosive device, which includes detonating powder, high explosive black powder, etc. Powder compaction is one of the most crucial …