Sensitive and selective detection of mercury (II) based on the aggregation of gold nanoparticles stabilized by riboflavin

Gold nanoparticles (AuNPs) can be stabilized by riboflavin against tris buffer-induced aggregation. However, in the presence of mercury (II) (Hg2+), riboflavin can be released from the AuNPs surface and the riboflavin-Hg2+ complex formed, leading to the aggregation of AuNPs in tris buffer. The aggregation extent depends on the concentration of Hg2+. Based on the aggregation extent, a simple and sensitive method of determining Hg2+ is developed. The method enables the detection of Hg2+ over the concentration range of 0.02-0.8 microM, with a detection limit (3sigma) of 14 nM, and shows excellent selectivity for Hg2+ over other metal ions (Cu2+, Co2+, Cd2+, Pb2+, Mg2+, Zn2+, Ag+, Ce3+, Ca2+, Al3+, K+). More importantly, the method avoids complicated surface modifications and tedious separation processes.     

孔隙率对氧化铝基可溶陶瓷型芯性能的影响

氧化铝基陶瓷型芯的可溶性是影响型芯应用于制造高性能燃机叶片的关键。研究了孔隙率对氧化铝基陶瓷型芯性能影响的规律。结果表明,型芯的溶失过程主要是莫来石相的溶失;型芯溶失性随着孔隙率的增加呈先增加后趋于稳定的变化规律,型芯强度则逐渐下降。当孔隙率为41.8%时溶失速率可达7.6mg/min,室温抗折强度超过14MPa;单次碱煮时间不宜超过4h。     

电子束焊喷射成形Al-Zn-Mg-Cu合金的组织性能研究

采用电子束焊接的方法对10 mm厚的喷射成形Al-Zn-Mg-Cu合金板进行了拼焊实验。采用金相显微镜、扫描电镜、室温拉伸实验、显微硬度等方法分析了焊接接头的微观组织,测试了焊接接头的力学性能及显微硬度。结果表明,喷射成形Al-Zn-Mg-Cu合金焊接接头由三个区域(近缝区母材,焊核区,热影响区)组成。焊缝宽为0.3～1.0 mm,焊核区由尺寸约3～8μm的等轴细晶组成,析出相沿晶界分布,晶内析出相较少;热影响区大部分保留了母材的原始组织特征,小部分区域发生了重熔。从焊缝区到母材,显微硬度值逐渐下降,焊缝区硬度值高出母材约35。经T6处理后,焊接接头强度约为母材的82%。     

Ti,B,RE联合细化细晶铝锭的工艺优化研究

通过两因素三水平的正交设计实验和极端顶点的混料设计实验,研究了不同含量的Ti,B,RE对细晶铝锭的联合细化效果;并根据正交设计实验的方差分析和混料设计实验非线性方程的最小二乘法求解,寻求Ti,B,RE联合细化的最优工艺。结果表明:正交设计和混料设计得到的最优工艺基本一致,即Ti=0.01%,B=0.001%,RE=0.1%,Ti/B=10/1,Ti/RE=1/10,且Ti/B对细化效果影响显著,而Ti/RE的影响次之。为了验证最优组合的细化效果,将0.01%Ti+0.1%RE+0.001%B的细晶铝锭、0.01%Ti的细晶铝锭、0.01%Ti+0.3%RE的细晶铝锭和0.01%Ti的A l-5Ti-1B分别细化6063铝合金,发现0.01%Ti+0.1%RE+0.001%B的细晶铝锭的细化效果最好。     

粉状矿体无底柱分段崩落采矿法大结构参数研究

针对粉状矿体工程地质特征,采用理论分析、数值模拟、物理模拟和现场放矿试验验证的研究体系,得到粉矿地段无底柱分段崩落采矿法合理大结构参数为14m×16m×3.4m。经现场应用,回收率达86.47%,矿石贫化率为21.65%,取得了较好的经济效益。粉状矿体地段无底柱分段崩落采矿法大间距结构模型,总体变化趋势是,总回收率、纯矿石回收率随着放矿步距的增大而增大,而岩石混入率则随着放矿步距的增大而减小;回收指标受放矿步距影响显著,在设备铲装能力许可的条件下,还可以进一步加大步距0.4m左右,即放矿步距为3.8m。     

Application of Innovative Critical Chain Method for Project Planning and Control under Resource Constraints and Uncertainty

This research proposes an innovative critical chain method (ICCM) for project planning and control under resource constraints and uncertainty. An improved genetic algorithm is developed to identify the critical chain and to obtain the optimal start time of each activity under the most optimistic duration of each activity and resource constraints. Furthermore, a feeding buffer is added in an insert point in order to deal with uncertainties. The benefits of applying this ICCM are demonstrated in an example project.     

Pressure effect on optical properties and structure stability of LaPO4:Eu(3+) microspheres

Uniform monoclinic core-shell and hexagonal urchin-like LaPO4:Eu(3+) spheres are synthesized via an attractive hydrothermal method owing to the higher yield and simplicity. Photoluminescence and Raman spectra of two samples have been investigated under high pressure up to 28 GPa using diamond anvil cells. At ambient pressure, both samples exhibit same luminescent properties with that of bulk monazite LaPO4:Eu(3+). With the increase of pressure, the emission intensity of Eu(3+) decreases and the half-widths of transition lines increase for both samples, while emission peaks show a red shift toward longer wavelengths due to increase in both the crystal-field strength and the covalency. Monoclinic core-shell LaPO4:Eu(3+) becomes amorphous finally while hexagonal urchin-like one transforms to monoclinic structure at lower pressure of 3.2 GPa and turns into amorphous structure at higher pressures, which are presented based on the analysis of high pressure Raman spectra.     

Study of Deformation Mechanisms in Titanium by Interrupted Rolling and Channel Die Compression Tests

The mechanisms of small plastic deformation of titanium (T40) during cold rolling and channel die compression by means of "interrupted in situ" EBSD orientation measurements were studied. These interrupted EBSD orientation measurements allow to determine the rotation flow field which leads to the development of the crystallographic texture during the plastic deformation. Results show that during rolling, tension twins and compression twins occur and various glide systems are activated, the number of grains being larger with twins than with slip traces. In channel die compression, only tension twins are observed in some grains, whereas slip traces can be spotted in almost all observed grains. The different stress conditions and different strain rates existing under the two modes of deformation lead to the activation of different deformation mechanisms.     

二维分数阶卡尔曼滤波及其在图像处理中的应用

该文研究了二维分数阶卡尔曼滤波及其在图像增强与滤波中的应用问题。首先基于分数微积分的定义,建立了二维线性离散系统的分数阶差分状态空间模型。然后,提出了一种可应用于图像信息处理的二维分数阶卡尔曼滤波算法,并通过实验验证了该文提出算法的有效性。仿真结果证明,该算法增强了图像中的细节特征,同时消弱了图像中的背景噪声。     

The influence of molecular weight on properties of melt-processable copolyimides derived from thioetherdiphthalic anhydride isomers

A series of novel melt-processable copolyimides based on mixed thioetherdiphthalic anhydride (TDPA) isomers and 4,4′-oxydianiline (4,4′-ODA) were synthesized by a one-step polycondensation. Molecular weight of copolyimides was controlled with stoichiometric offsets in favor of 4,4′-ODA. All of the resulting polyimides (PIs) were amorphous and have nice solubility. With increase in molecular weight, the glass transition temperatures of copolyimides increased from 248 to ca. 270 °C based on DSC measurements. These copolyimides displayed excellent thermal and thermooxidative stability, as evidenced by thermogravimetric analysis in both air and nitrogen atmospheres. The melt processability, thermoplastic response, melt stability, and their dependence on molecular weight of the copolyimides have been investigated in terms of rheological measurements by monitoring the melt viscosity after residence at various times and temperatures.