The interface chemistry between chalcogenide clusters and open framework chalcogenides

One of the most exciting recent developments concerning molecular architectures is the emerging field of crystalline chalcogenide superlattices that bridges two traditional but distinct areas of research: chalcogenide clusters and porous materials. By combining synthetic and structural concepts in these two areas, many crystalline solids containing spatially organized chalcogenide clusters have been created that exhibit varied properties ranging from microporosity, fast ion conductivity, and photoluminescence to narrow and tunable electronic band gaps. The potential applications of these materials extend beyond traditional areas such as acid catalysis or adsorption-based separation to include shape- or size-selective photocatalysis, solid-state ionics, and electrochemistry.     

CK3MCuN钢各元素分析曲线的制作

使用布鲁克Q8直读光谱仪分析CK3MCuN钢的化学成分。制作CK3MCuN钢化学元素的工作曲线,并合理设定干扰元素,使分析结果准确稳定,满足生产的需要。     

ZrTiO4材料的合成与性能结构研究

以TiO2、ZrO2为主要原料,以MgO、SiO2、CaO为添加剂,在1 500℃、1 550℃、1 600℃各保温3 h烧成制得ZrTiO4材料,研究了各添加剂及温度对ZrTiO4材料的合成与性能的影响.试验结果发现:ZrTiO4材料较为适宜的合成温度为1550℃,各材料试样具有较高的体积密度和抗折强度.添加剂为CaO的ZT-C试样的体积密度为4.54g/cm3,抗折强度为102 MPa,适于用作高温领域的结构材料.     

Behaviour of bone origin hydroxyapatite at elevated temperatures and in O2 and CO2 atmospheres

In the present work the behaviour of HAp extracted from pig bones at elevated temperatures up to 1000 °C in O₂ and CO₂ atmospheres has been studied. It has been found that CO₂ atmosphere arrests HAp decomposition. Chemical analysis and infrared spectroscopy reveal that no free CaO appears and no decrease of CO₃⁻² group concentration occurs in the material calcined in CO₂ atmosphere. In the O₂ atmosphere at elevated temperatures, CaO and CO₂ are emitted from the samples, although the remaining material retains the HAp structure as indicated by the X-ray diffraction.     

Synthesis and electrostatic assembly of an optically active derivative of poly(ethylene-alt-maleic anhydride) with l-phenylalanine as a chiral material

The layer-by-layer (LbL) assembly of polyelectrolytes is an excellent method for the fabrication of functional ultra-thin multilayers. The functional properties of the film depend on the nature of the polyelectrolyte. Thus, to develop new applications for LbL multilayer films, it is first necessary to synthesize new functional polyelectrolytes. We have prepared a novel, optically active polyelectrolyte, an l-phenylalanine derivative of poly(ethylene-alt-maleic anhydride) (PEMA-l-Phe), via ring-opening of the succinic anhydride unit. We have characterized this polyelectrolyte by FTIR, UV–Vis spectroscopy, ¹H NMR, and polarimetric analysis. The specific rotatory power, [α]_D, of the chiral polymer was ?101.3°, greater than that of l-phenylalanine (?35.1°). We fabricated an ultra-thin film of (PEMA-l-Phe)/poly(allylamine hydrochloride) (PAH) with the electrostatic LbL self-assembly method. The assembly of this ultra-thin film was monitored with a UV–Vis spectrophotometer. The results indicate that the absorbance of the multilayer at 210 nm grows exponentially with the number of bilayers, and that the mass of each bilayer is 1.263 times that of the previous bilayer. This multilayer has potential applications in chiral identification and separation.     

Synthesis and characterization of phenylene-thiophene all-conjugated diblock copolymers

Grignard metathesis (GRIM) polymerization for all-conjugated diblock copolymers comprising poly(2,5-dihexyloxy-1,4-phenylene) (PPP) and poly(3-hexylthiophene) (P3HT) blocks were systematically studied with LiCl as additive and 1,2-bis (diphenylphosphino) ethane nickel dichloride (Ni(dppe)Cl₂) or 1,3-bis(diphenylphosphino) propane nickel dichloride (Ni(dppp)Cl₂) as catalyst. It was found that the addition order of the monomers was crucial for the success of copolymerization. With the monomer addition in the order of phenyl and then thienyl Grignard reagents, all-conjugated PPP-b-P3HT diblock copolymers with different block ratios were successfully synthesized. In contrast, the inverted addition order only afforded a mixture containing both block copolymers and deactivated or end-capped homopolymers. Mass spectroscopic analysis indicates that the effect of the addition order of the monomers on copolymerization is attributed to the low efficiency of intramolecular Ni transfer from thiophene to phenylene units. The resulting PPP-b-P3HT diblock copolymers were characterized by differential scanning calorimetry (DSC) and atomic force microscopy (AFM). It was found that both PPP and P3HT blocks in the copolymers were crystalline, and microphase separation between them took place, as indicated by two endothermal transitions corresponding to the melting of PPP and P3HT blocks, respectively. These unique properties may render PPP-b-P3HT diblock copolymers potential applications in optoelectronics.     

Maximum likelihood estimation of higher‐order integer‐valued autoregressive processes

Abstract. In this article, we extend the earlier work of Freeland and McCabe [Journal of time Series Analysis (2004) Vol. 25, pp. 701–722] and develop a general framework for maximum likelihood (ML) analysis of higher‐order integer‐valued autoregressive processes. Our exposition includes the case where the innovation sequence has a Poisson distribution and the thinning is binomial. A recursive representation of the transition probability of the model is proposed. Based on this transition probability, we derive expressions for the score function and the Fisher information matrix, which form the basis for ML estimation and inference. Similar to the results in Freeland and McCabe (2004) , we show that the score function and the Fisher information matrix can be neatly represented as conditional expectations. Using the INAR(2) specification with binomial thinning and Poisson innovations, we examine both the asymptotic efficiency and finite sample properties of the ML estimator in relation to the widely used conditional least squares (CLS) and Yule–Walker (YW) estimators. We conclude that, if the Poisson assumption can be justified, there are substantial gains to be had from using ML especially when the thinning parameters are large.     

毛细管区带电泳在生物农药残留分析中的应用

毛细管电泳(CE)具有所需样品量小、分离效率高等特点,已经引起越来越多的关注,并将它应用到农药残留的检测中。对目前的多种检测方法的优缺点及其在农药残留检测中的应用情况进行了综述,同时介绍了生物农药的毛细管区带电泳(CZE)的检测情况,展望了CZE在农药残留分析与检测中的应用前景。     

A magnetic sensor array for spot welding quality monitor

Spot welding is affected by many factors and is difficult to monitor the nugget information with single sensor. In this paper, a new monitor system based on sensors array technique was developed for spot welding quality detection. The key part in the system is cross magnetic sensor array. It is composed of six magnetic sensors. An improved algorithm was proposed to extract the signal eigenvalue, which was based on principle component analysis. The results show that in the case of the 60 mm experiment, cross magnetic sensor array works well. And when the eigenvalues range of the cross magnetic sensor array is 0.090 1-0.098 2, the spots quality is good. The analysis of the eigenvalues of the cross magnetic sensor array allows us to determine whether the spot quality is good or bad.     

SiO2基复合隔热材料制备及其性能研究

通过静电纺丝技术制备出柔性SiO2纳米纤维,将其与亲水型气相SiO2混合均匀后,采用半干法压制得到SiO2复合隔热材料.研究结果表明,柔性SiO2纤维为亲水型气相SiO2提供了空间网络骨架,在未明显提高其导热系数的基础上提高了其抗折强度.