Effects of relative positioning of energy sources on weld integrity for hybrid laser arc welding

This study is concerned with the effects of laser and arc arrangement on weld integrity for the hybrid laser arc welding processes. Experiments were conducted for a high-strength steel using a 4 kW Nd: YAG laser and a metal active gas (MAG) welding facility under two configurations of arc–laser hybrid welding (ALHW) and laser–arc hybrid welding (LAHW). Metallographic analysis and mechanical testing were performed to evaluate the weld integrity in terms of weld bead geometry, microstructure and mechanical properties. The morphology of the weld bead cross-section was studied and the typical macrostructure of the weld beads appeared to be cone-shaped and cocktail cup-shaped under ALHW and LAHW configurations, respectively. The weld integrity attributes of microstructure, phase constituents and microhardness were analyzed for different weld regions. The tensile and impact tests were performed and fracture surface morphology was analyzed by scanning electron microscope. The study showed that ALHW produced joints with a better weld shape and a more uniform microstructure of lath martensite, while LAHW weld had a heterogeneous structure of lath martensite and austenite.     

Thermodynamics of binary and ternary interactions in the tin(II)/phytate system in aqueous solutions,in the presence of Cl− or F−

An extensive study of the tin(II)/phytate (Phy) system was carried out in NaNO_3(aq), at different ionic strengths (0.10 ⩽ I/mol · L⁻¹ ⩽ 1.00) and temperatures (278.15 ⩽ T/K ⩽ 328.15), by potentiometric and voltammetric techniques. The stability and formation enthalpy changes of six SnH_qPhy species were determined. To better characterise this system, some potentiometric titrations were also carried out in mixed ionic media (NaNO_3(aq) + NaCl_(aq) and NaNO_3(aq) + NaF_(aq)) at total ionic strength I = 1.00 mol · L⁻¹. The formation of some ternary mixed SnH_qPhyCl and SnH_qPhyF species (charges omitted for simplicity) was found. The formation enthalpies of the complex species were calculated, at I = 0.40 mol · L⁻¹ in NaNO_3(aq), by the dependence of stability constants on temperature obtained by potentiometric titrations, in the range 278.15 ⩽ T/K ⩽ 328.15. The complex formation process is endothermic, and the main contribution to tin(II) complexation by phytate is entropic in nature. For example, for the SnPhy species we have, at T = 298.15 K and I = 0.40 mol · L⁻¹ in NaNO_3(aq): ΔH = 57.7 ± 2.8 kJ mol · L⁻¹, ΔG = −99.9 ± 1.7 kJ mol · L⁻¹, and TΔS = 158 ± 3 kJ mol · L⁻¹. The ionic strength dependence of the formation constants of the simple tin(II)/phytate species, was modelled by the Debye–Hückel and the SIT approaches. The sequestering ability of phytate towards tin(II) was evaluated by calculating the pL_0.5 values (i.e., the total ligand concentration necessary to bind 50% of cation present in trace) at different ionic strengths, ionic media, and pH. The sequestering ability increases with increasing the pH, whilst it decreases with increasing the ionic strength (the same behaviour shown by the stability constants). Moreover, taking into account the different sequestering ability of phytate towards tin(II) in the different ionic media, the trend: pL_0.5 = 5.70 (in NaNO_3(aq) + NaF_(aq)) > pL_0.5 = 5.16 (in NaNO_3(aq) + NaCl_(aq)) > pL_0.5 = 4.86 (in NaNO_3(aq)) was observed at pH 8.1 and I = 1.00 mol · L⁻¹. This is due to the presence of a second ligand (Cl⁻ or F⁻) that stabilizes the complex species with the formation of ternary complex species. Some empirical relationships were also found.     

5-(二甲基氨基)-N-(4-(2-(2-羟基亚苄基)甲酰肼基)苯基)萘-1-磺酰胺的合成及对锌离子识别的光谱性能研究

合成了含有丹磺酰胺荧光团的新型Zn2+荧光探针DH1(5-(二甲基氨基)-N-(4-(2-(2-羟基亚苄基)甲酰肼基)苯基)萘-1-磺酰胺),利用光谱法研究它对锌离子的识别作用。光谱滴定和ESI-MS谱分析表明DH1与Zn2+以1∶1的化学计量数配位。在CH3CN/H2O(φ,9∶1)体系中,DH1与Zn2+结合后荧光显著增强,量子产率高达0.53,荧光检测限达到1.0×10-7 mol.L-1,而其他常见金属离子,如K+,Li+,Na+,Mg2+,Ca2+,Cr3+,Mn2+,Ni 2+,Pb2+,Cu2+,Cd2+,Co2+,Fe2+及Hg2+不引起荧光光谱变化。结果表明,DH1对锌离子识别具有较高的选择性和灵敏度。     

Spectroscopic investigation on the sonodynamic activity of Safranine T to bovine serum albumin damage

In this paper, the Safranine T (ST) was used as sonosensitive compound to study the sonodynamic damage to bovine serum albumin (BSA) under ultrasonic irradiation using fluorescence and UV–vis spectroscopy. The experimental results revealed the obvious synergetic effect of Safranine T (ST) and ultrasonic irradiation during the damage of BSA molecules. In addition, some influencing factors such as ultrasonic irradiation time, Safranine T (ST) concentration, pH value and ionic strength on the sonodynamic damage of BSA molecules were also considered. Finally, the generation of reactive oxygen species (ROS) in sonodynamic process was estimated by the method of Oxidation-Extraction Photometry (OEP). Meanwhile, several radical scavengers were used to determine the kind of generated ROS. Experiments showed that under ultrasonic irradiation the Safranine T (ST) can generate several kinds of ROS at the same time, at least including singlet oxygen (¹O₂) and hydroxyl radicals (OH).     

新型锌离子荧光探针(5-(二甲基氨基)-N-(4-(2-(2-喹啉亚甲基)甲酰肼基)苯基)萘-1-磺酰胺)的研究

以丹磺酰胺为荧光基团设计合成了新型Zn²⁺荧光探针DW1(5-(二甲基氨基)-N-(4-(2-(2-喹啉亚甲基)甲酰肼基)苯基)萘-1-磺酰胺)。通过紫外光谱、荧光光谱及电喷雾质谱研究了DW1对Zn²⁺的选择性识别作用。结果表明,DW1与Zn²⁺结合后荧光显著增强,荧光发射光谱由545 nm蓝移至515 nm,量子产率达到0.32,且对Zn²⁺具有较高的选择性,受常见离子的干扰较小。光谱滴定和ESI-MS谱表明DW1与Zn²⁺以1∶1的化学计量数形成配合物,平衡常数K=1.75×10⁴(mol/L)^-1。     

替米沙坦与氯冉酸的荷移反应

用分光光度法研究了替米沙坦与氯冉酸的电荷转移反应条件,替米沙坦与氯冉酸在丙酮溶液中可以发生电荷转移反应,在室温下按实验方法配好溶液即可比色。电荷转移络合物的最大吸收波长是525nm,表观摩尔吸光系数为2.18×10²L·mol^-1·cm^-1。替米沙坦质量浓度在16—192mg·L^-1范围内服从比耳定律,相关系数为0.9997。当替米沙坦浓度为80mg·L^-1时,六次测定结果的相对标准偏差为1.33%,回收率在99.0%以上。测得荷移络合物的组成和稳定常数分别为1:2和3.9×10⁷。用于测定制剂中替米沙坦的含量结果令人满意。     

半无爪可迹图的度和条件

可迹图即为一个含有Hamilton路的图.令$N[v]=N(v)\cup\{v\}$, $J(u,v)=\{w\in N(u)\cap N(v):N(w)\subseteq N[u]\cup N[v]\}$.若图中任意距离为2的两点$u,v$满足$J(u,v)\neq \emptyset$,则称该图为半无爪图.令$\sigma_{k}(G)=\min\{\sum_{v\in S}d(v):S$为$G$中含有$k$个点的独立集\},其中$d(v)$表示图$G$中顶点$v$的度.本论文证明了若图$G$为一个阶数为$n$的连通半无爪图,且$\sigma_{3}(G)\geq {n-2}$,则图$G$为可迹图; 文中给出一个图例,说明上述结果中的界是下确界; 此外,我们证明了若图$G$为一个阶数为$n$的连通半无爪图,且$\sigma_{2}(G)\geq \frac{2({n-2})}{3}$,则该图为可迹图.     

The double-effect mechanism between Fe3O4 nanoparticles and MSA-capped CdTe QDs

Water-soluble mercaptosuccinic acid (MSA)-capped CdTe quantum dots (QDs) of two sizes and superparamagnetic Fe₃O₄ nanoparticles have been synthesized and used to investigate the effect of the mechanism of Fe₃O₄ nanoparticles on the fluorescence intensity of QDs. In the presence of a low concentration of Fe₃O₄ nanoparticles, the CdTe QDs with smaller particle size exhibit fluorescence quenching while fluorescence enhancement of CdTe QDs with larger particle size was observed, and the fluorescence intensity changes with the excitation wavelength and the concentration of Fe₃O₄ nanoparticles. The mechanism study shows that there is a double-effect between the Fe₃O₄ and CdTe QDs: one is the fluorescence quenching effect due to Fe₃O₄ strong absorption of excitation and emission light, the other is the fluorescence enhancement effect resulting from a localized electromagnetic field caused by the absorption of exciting light. The fluorescence of CdTe QDs with lower concentration of Fe₃O₄ nanoparticles was determined via the synergy of the double-effect. To our best knowledge, this is the first systematic study on the interaction between Fe₃O₄ nanoparticles and CdTe QDs, which finds the fluorescence enhancement effect in the presence of low concentration of Fe₃O₄.     

纳米氧化钛团聚结构的研究

爆轰形成的高温、高压持续时间短,使得新生的氧化钛来不及长成较大的晶粒,只能形成大量的类球形纳米微粒。在潮湿的爆生气体环境中,这些纳米氧化钛颗粒间的相互作用(如碰撞、摩擦、挤压、渗透和粘附等)比较剧烈,极易聚集成团聚体。初步分析了以硫酸氧钛为钛源、采用爆轰法合成的纳米氧化钛的团聚结构和分散形态,对经过加热至500℃、保温1 h热处理后的纳米氧化钛的团聚结构也进行了分析。研究结果表明:用爆轰法合成的纳米氧化钛存在软团聚和硬团聚两种形式,而经过热处理(500℃、1 h)的纳米氧化钛的团聚程度得到了一定的改善。此外,还分析了纳米粉体的特性、爆轰特点和爆生气体环境等因素对产生纳米氧化钛团聚结构的影响。     

香菇中甲醛的提取与测定

用乙酰丙酮分光光度法测定香菇在不同温度下浸泡不同时间的浸出液中甲醛含量,实验结果表明,用60℃的水浸泡40min或40℃的水浸泡60min可最大限度浸出香菇中的甲醛,为健康食用香菇提供理论依据。