Robust and Tunable Ferroelectricity in Ba/Co Codoped (K_(0.5)Na_(0.5))NbO_(3) Ceramics

The 0.98(K_(0.5)Na_(0.5))NbO_(3)-0.02Ba(Nb_(0.5)Co_(0.5))O_(3-δ) ceramics with doped Ba^(2+) and Co^(2+) ions are fabricated,and the impacts of the thermal process are studied.Compared with the rapidly cooled (RC) sample,the slowly cooled (SC) sample possesses superior dielectric and ferroelectric properties,and an 11 K higher ferroelectricparaelectric phase transition temperature,which can be attributed to the structural characteristics such as the grain size and the degree of anisotropy.Heat treatment can reversibly modulate the content of the oxygen vacancies,and in turn the ferroelectric hysteresis loops of the samples.Finally,robust and tunable ferroelectric property is achieved in SC samples with good structural integrity.

不同力度屏蔽蓝光对正常成年人眼视功能的影响

目的：探索不同程度屏蔽420．460nm波段蓝光镜片对人眼视功能的防护作用。方法：自身对照研究。2016年8月至2017年3月选择来自同济大学的健康大学生志愿者20例，先后在未戴镜，配戴屏蔽20％、30％、40％、60％防蓝光护目镜下，完成24个色区辨识评分和75min阅读任务。检测调节幅度、品状体调节力等指标，并做视疲劳问卷评分。采用配对秩和检验对各组数值进行分析。结果：配戴屏蔽30％、40％和60％防蓝光护目镜和未戴镜比较时，多个色区得分均低于未戴镜（P〈0．05）；而屏蔽20％与未戴镜比较，差异均无统计学意义。完成阅读任务后，在视疲劳调查问卷总得分上，屏蔽20％、30％、40％、60％蓝光得分低于未戴镜（均P〈0．05）。在用眼前后单眼调节幅度差值上、正相对调节差值上，屏蔽20％、30％、40％、60％蓝光变化幅度小于与未戴镜（均P〈0．05）；在用眼前后负相对调节差值上，40％、60％蓝光变化幅度小于未戴镜（P〈0．05）；屏蔽20％、30％蓝光和未戴镜比较差异无统计学意义。在用眼前后晶状体调节力差值上，屏蔽20％、30％、40％、60％蓝光和未戴镜相比差异无统计学意义。结论：屏蔽蓝光的波段以440nm为中心，带宽20nm，屏蔽力度20％以上时，可以改善人眼调节力、视疲劳主观症状。但屏蔽该段蓝光力度达30％以上时，会造成色差症状。

High ammonia sensitive ability of novel Cu12Sb4S13 quantum dots@reduced graphene oxide nanosheet composites at room temperature

In the work,rGO nanosheet is synthesized using the typical Hummer’s method,then Cu12Sb4 S13 quantum dots@rGO composites are prepared by solvent thermal method,and Cu12Sb4 S13 quantum dots with the average size of 5 nm are densely distributed on the surface of rGO sheet.NH3 gas response of Cu12Sb4 S13quantum dots@rGO nanosheet composites at room te mperature of 25℃is enhanced compared with the pure Cu12Sb4 S13 quantum dots and rGO nanosheet,and the composites possess an excellent stability during the humidity range of 45%-80%with a low detection limit of 1 ppm,which is related with the intrinsic hydrophobicity characteristic of Cu12Sb4 S13 quantum dots.It also proves that Cu12Sb4 S13quantum dots@rGO nanosheet composites have a quite high selectivity towards ammonia compared with ethanol,methanol,acetone,toluene,hydrogen sulfide and nitrogen dioxide at room temperature.The gas sensing mechanism of the composites is discussed primarily.