排序方式: 共有15条查询结果,搜索用时 15 毫秒
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在SnBi36Ag0.5无铅焊料合金的基础上,添加Ce元素,研究Ce含量对合金显微组织、熔化特性、润湿性和力学性能的影响。按质量比将纯Sn球、Bi锭、Ag锭和中间合金SnCe1.8在400℃熔化,保温6 h。搅拌均匀后在320℃浇铸,制备成SnBi36Ag0.5Cex(x=0%,0.03%,0.07%,0.1%,0.3%)焊料合金。通过X射线衍射仪对合金进行物相分析,通过扫描电镜(SEM-EDS)和光学金相显微镜(OM)分析焊料合金的显微组织,通过差示扫描量热分析仪(DSC)表征焊料合金熔化特性,通过可焊性测试仪表征焊料的润湿性,采用万能材料试验机测试焊料合金的力学性能。结果表明:Ce能起到细化组织的作用使脆硬的富Bi相更加细小均匀。Ce的添加会导致熔点和熔程有轻微上升。当Ce含量为0.07%时润湿时间最短,润湿力最大,综合润湿性最佳。当Ce含量为0.07%时有最高的抗拉强度和延伸率。 相似文献
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以罗丹明酰肼和三聚氯氰缩合反应所得罗丹明-三嗪衍生物R1作为荧光探针,通过紫外光谱、荧光光谱、红外光谱和质谱方法研究了该探针的识别性能。结果表明:在乙腈-水(1∶1,V/V,Tris-HCl,0.02 mol/L,pH 7)介质中,探针R1能选择性、可逆识别Cu~(2+)。识别机制是基于Cu~(2+)的加入使探针R1分子内的内酰胺环结构打开,形成1∶1络合物,产生强荧光,同时伴随从无色到紫红色的明显颜色变化。据此,制备了基于R1的Cu~(2+)检测试纸,可以方便快捷地检测水中的Cu~(2+);此外,利用细胞成像技术在He La细胞内实现了对Cu~(2+)的荧光显微成像,为生物体活细胞内Cu~(2+)的检测提供了重要的方法参考。 相似文献
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The equation of state(EoS) of dark energy plays an important role in the evolution of the universe and has attracted considerable interest in the recent years. With the progress in observational technique, a precise constraint on the EoS of dark energy can be obtained. In this study, we reconstruct the EoS of dark energy and cosmic expansion using Gaussian processes(GP) from the most up-to-date Pantheon compilation of type Ia supernovae(SNe Ia),which consists of 1048 finely calibrated SNe Ia. The reconstructed EoS of dark energy has a large uncertainty owing to its dependence on the second-order derivative of the construction. Adding the direct measurements of Hubble parameters H(z) as an additional constraint on the first-order derivative can partially reduce the uncertainty; however, it is still not sufficiently precise to distinguish between the evolving and the constant dark energy. Moreover, the results heavily rely on the prior of the Hubble constant H0. The H0 value inferred from SNe+ H(z) without prior is H0= 70.5 ± 0.5 km s~(-1) Mpc~(-1). Moreover, the matter density ?M has a non-negligible effect on the reconstruction of dark energy. Therefore, more accurate determinations on H_0 and ?_M are required to tightly constrain the EoS of dark energy. 相似文献
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为了实现在侧边抛磨光纤(SPF)上制作布拉格光栅结构并提高器件设计灵活性,利用重铬酸盐明胶(DCG)作为光刻材料,提出一种新型的光纤表面布拉格光栅制作方法并对该器件温度传感特性进行研究。使用轮式抛磨系统制作SPF,并在SPF侧抛面上旋涂DCG,通过干涉光束曝光显影制作表面布拉格光栅。光谱测量表明:带有布拉格光栅的侧边抛磨光纤在1 480.2 nm处有透射谷,在相应位置反射谱有明显反射峰,其调制幅度达到15.9 dB,这是由于表面光栅的布拉格反射所致。温度传感实验表明,该布拉格反射峰的温度灵敏度为17.84 pm/℃。这种器件已在光纤传感和光纤滤波器等方面获得应用。 相似文献
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三种植物对铀耐性及土壤中铀吸收积累差异的研究 总被引:5,自引:0,他引:5
采用溶液培养结合土壤培养的方法,研究了小白菜、冬苋菜和菠菜对铀的耐性及土壤中铀吸收积累的差异.结果表明:水培条件下(U 50mg/L),与小白菜和冬苋菜相比,菠菜对铀具有较强的耐性;在100mg/kg 土U的条件下,菠菜表现出比小白菜和冬苋菜更高吸收和积累铀的能力,其地上部分铀含量为232mg/kg DW(Dry Weight 干重),而根部铀含量达433mh/kg DW(Dry Weight 干重).菠菜可能对铀污染土壤的植物修复具有潜在的应用价值. 相似文献
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研究了分别添加γ-聚谷氨酸(γ-PGA)及1,4,7,10-四杂环十二烷基四乙酸(DOTA)的两种明胶膜对Am(Ⅲ)/Eu(Ⅲ)的吸附行为。结果表明,添加γ-PGA的明胶膜,在2.0 mol/L硝酸介质中,γ-PGA∶明胶的质量比为1∶5、吸附时间在15h以上时,对Eu3 的吸附率达38.6%,而对Am3 基本不吸附;添加DOTA的明胶膜,在2.0 mol/L硝酸介质中,DOTA∶明胶的质量比为1∶5、吸附时间在15h以上时,对Am3 的吸附率达41.3%,而对Eu3 的吸附率为5.1%。 相似文献
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We constrain three cosmological models,i.e.,ACDM model, holographic dark energy(HDE) model and R_h = ct model by using the recent Pantheon compilation of type la supernovae(SN la), the direction measurements of Hubble parameter H(z), and the baryon acoustic oscillations(BAO). The spatial curvature is considered in the ACDM model and the HDE model. We show that the HDE model in a spatially flat and HDE dominate universe has the same behavior as Rh = ct model if the characteristic parameter of the HDE model C_0 approaches to infinity. Numerical results show that the ACDM model is the best favoured one among the three models. The HDE model is consistent with observational data, the best fitting value of C_0 is around 0.8, which implies that the Rh = ct model should be modified to be compatible with the present cosmological observational data. Combing all the datasets, we give strict constraint on the Hubble constant,where h_0=0.694 ± 0.020 for the ACDM model and h_0= 0.689 ±0.019 for the HDE model.Our results imply that the tension of Hubble constant between Planck collaborations and Riess et al. has been partially relaxed. The constraint on the spatial curvature is also given,where Ω_(k0) =-0.066 ± 0.165 for the ACDM model andΩ_(k0)=0.029 ± 0.067 for the HDE model. 相似文献
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The possible variation of the electromagnetic fine structure constant, αe, at cosmological scales has aroused great interest in recent years. Strongly lensed gravitational waves(GWs) and their electromagnetic counterparts could be used to test this variation. Under the assumption that the speed of a photon can be modified,whereas the speed of a GW is the same as predicted by general relativity, and they both propagate in a flat FriedmanRobertson-Walker universe, we investigated the difference in time delays of the images and derived the upper bound of the variation of αe. For a typical lensing system in the standard cosmological models, we obtained B cosθ 1.85×10~(-5),where B is the dipolar amplitude and θ is the angle between observation and the preferred direction. Our result is consistent with the most up-to-date observations on αe. In addition, the observations of strongly lensed GWs and their electromagnetic counterparts could be used to test which types of alternative theories of gravity can account for the variation of α_e. 相似文献
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