A new method for information retrieval in two-dimensional grating-based X-ray phase contrast imaging

Grating-based X-ray phase contrast imaging has been demonstrated to be an extremely powerful phase-sensitive imaging technique.By using two-dimensional(2D) gratings,the observable contrast is extended to two refraction directions.Recently,we have developed a novel reverse-projection(RP) method,which is capable of retrieving the object information efficiently with one-dimensional(1D) grating-based phase contrast imaging.In this contribution,we present its extension to the 2D grating-based X-ray phase contrast imaging,named the two-dimensional reverseprojection(2D-RP) method,for information retrieval.The method takes into account the nonlinear contributions of two refraction directions and allows the retrieval of the absorption,the horizontal and the vertical refraction images.The obtained information can be used for the reconstruction of the three-dimensional phase gradient field,and for an improved phase map retrieval and reconstruction.Numerical experiments are carried out,and the results confirm the validity of the 2D-RP method.     

具有超顺磁和可见/近红外发光性质的双功能介孔磁/光纳米复合材料

合成了两种双功能介孔磁/光纳米复合材料。磁性Fe3O4纳米粒子作为核被包覆于介孔二氧化硅纳米球中,稀土铽和铒配合物分别通过硅烷化的配体PABA-Si和phen-Si共价嫁接于介孔球的网络中。研究了所制备的双功能纳米复合材料的结构、磁性、荧光发射性质,结果表明,双功能纳米复合材料具有介孔结构、超顺磁特性和相应稀土配合物的特征荧光发射性质。     

电动汽车热泵系统中易燃制冷剂R290的燃烧特性

研究了制冷剂R290在电动汽车热泵空调系统潜在泄漏过程中的燃烧特性,通过实验得到了不同泄漏温度和体积流量下R290的燃烧特性,并与制冷剂R134a进行对比。实验表明:R290在低温下更难点燃,而在高泄漏体积流量下和高泄漏温度下会发生喷射火焰的吹灭现象,且当泄漏温度在30~60℃之间时,泄漏体积流量的增大会提高其燃烧强度。R290制冷剂气体温度越高,其火焰燃烧强度越大,燃烧火焰越细,火焰心高度越低;R290制冷剂气体的体积流量越大,火焰燃烧区域越大,火焰高度越低,热辐射通量越大。