Li Xiao-Lin

Neutron activation analysis after a nickel sulphide fire assay preconcentration for determination of all platinum group elements in rocks

Neutron activation analysis after a nickel sulphide fire assay preconcentration for platinum group elements (PGE) has been established in our laboratory. In this work, the all PGE in DZ∑-2, a Chinese certified ultramafic rock standard reference material, are determined for testing the accuracy and precision of the method. The experimental conditions and the blank values from reagents and detection limits for the method are also presented.

Morphology, microstructure and chemical composition of single inhalable particles in Shanghai, China

The morphology, microstructure, and chemical composition of a variety of particles emitted from coal-fired power plants, steel plants, and vehicle exhausts, which are possible sources of particulate matter (PM) in the atmosphere, were investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) and compared with particle samples collected from urban atmosphere to identify the best footprint or the suitable indicator relating the existence of studied particles and their possible emitters by the morphology, microstructure, and chemical composition of the particles. The investigation indicated that the particles from these three sources are different in morphology, microstructure, and chemical composition. Sphere aggregates were generally the most abundant components, with silicon and aluminum as major elements. The urban air particulate contained particles similar to those observed in the power plant, steel plant, and vehicle exhaust samples suggesting that all three sources are contributing to the pollution in the city.

A meshless algorithm with moving least square approximations for elliptic Signorini problems

Based on the moving least square (MLS) approximations and the boundary integral equations (BIEs), a meshless algorithm is presented in this paper for elliptic Signorini problems. In the algorithm, a projection operator is used to tackle the nonlinear boundary inequality conditions. The Signorini problem is then reformulated as BIEs and the unknown boundary variables are approximated by the MLS approximations. Accordingly, only a nodal data structure on the boundary of a domain is required. The convergence of the algorithm is proven. Numerical examples are given to show the high convergence rate and high computational efficiency of the presented algorithm.

Surface Planar Ion Chip for Linear Radio-Frequency Paul Traps

We propose a surface planar ion chip which forms a linear radio frequency Paul ion trap. The electrodes reside in the two planes of a chip, and the trap axis is located above the chip surface. Its electric field and potential distribution are similar to the standard linear radio frequency Paul ion trap. This ion trap geometry may be greatly meaningful for quantum information processing.

Data Model and Virtual Database Engine for Grid Environment

There are many challenges of data sharing both in grid environment and traditional data integration domains, such as sharing between heterogeneous, distributed data sources. In grid environment, there are many specific features: limited data sharing, frequently changing data sources and large amounts of concurrent users. Under these conditions, it is strongly needed to provide more usable, more flexible system software and unique application programming interfaces to solve these problems. Vega information grid team has provided REVP data model and invented a flexible schema mapping tool employing reference technique to achieve these goals. In addition, performance in grid environment is especially important and needs some different optimization strategy. VIG has taken some optimization measures to improve the performance for distributed query. This paper elaborates the REVP data model and virtual database engine. Performance test shows that the query optimization measures are effective.

Interference by neutron induced second order nuclear reaction in activation analysis of platinum group elements after a nickel sulphide fire assay preconcentration

In determining the trace platinum group elements and gold in rocks and ores by the neutron activation analysis after a nickel sulphide fire assay preconcentration, there are interferences due to nuclides produced from second order nuclear reactions. This paper presents the degree of interference calculated over the ranges of long irradiation times and of reactor neutron flux from 1·1013 to 1·1015 n·cm−2·s−1. According to the results of these calculations, every one of the second order interfering reactions on the PGE+Au, except the197Au(n, γ)198Au(n, γ)199Au reaction, can be neglected under the long irradiation time or high reactor neutron flux. Special attention is given to the interference from gold in the determining platinum.

Structures and Hydrogen Storage Properties of La1-xMgxNi4.25Al0.75 (x=0.0, 0.1, 0.2, 0.3) Alloys

Abstract La1-xMgxNi4.25Al0.75 (x=0.0, 0.1, 0.2, 0.3) hydrogen storage alloys were prepared by a three-step induction melting. Their crystal structures and hydrogen storage properties were investigated. Results show that alloys with x=0.0 and 0.1 contain a single LaNi4Al phase; however, those with x=0.2 and 0.3 are composed of LaNi4Al, (La, Mg)Ni3 and AlNi3 phases. With x increasing from 0.2 to 0.3, the abundances of the secondary phases and the plateau pressures in the pressure-composition isotherms are lifted significantly. Meanwhile, their hydrogen storage capacities are remarkably reduced. It is found that the alloy with x=0.1 possesses the fastest absorption kinetics compared to the others as well as a good hydrogen capacity and a low plateau pressure.

Archimedean-Spiral-Based Microchip Ring Waveguide for Cold Atoms

We present a scheme for generating a ring magnetic waveguide on a single-layer atom chip. The wire layout consists of two interleaved Archimedean spirals of the same size. The waveguide avoids the trapping perturbation caused by the input and output ports, resulting in an enclosed guiding loop for neutral atoms in weak-field seeking states. Such a configuration can create a tight and deep trap potential with a small current. Taking the |F = 2, mF = 2〉 state of 87Rb as an example, the trap frequency and depth are estimated to be 18 kHz and 335 μK, respectively, with a dc current of 2 A.

Bose--Einstein condensation on an atom chip

We report an experiment of creating Bose-Einstein condensate (BEC) on an atom chip. The chip based Z-wire current and a homogeneous bias magnetic field create a tight magnetic trap, which allows for a fast production of BEC. After an 4.17s forced radio frequency evaporative cooling, a condensate with about 3000 atoms appears. And the transition temperature is about 300nK. This compact system is quite robust, allowing for versatile extensions and further studying of BEC.This paper reports an experiment of creating Bose?Einstein condensate (BEC) on an atom chip. The chip-based Z-wire current with a homogeneous bias magnetic field creates a tight magnetic trap, which allows for a fast production of BEC. After a 4.17-s forced radio frequency evaporative cooling, a condensate with about 3000 atoms appears. The transition temperature is about 300 nK. This compact system is quite robust, allowing for versatile extensions and further studying of BEC.

Trapping of neutral Rb-87 atoms on an atomchip

We report an experiment of trapping of neutral Rb-87 atoms on a, self-made atomchip. The H-shaped atomchip is made by magnetron sputtering technology, which is different from the atomchip technology of other teams. We collect 3 x 10(6) Rb-87 atoms in the mirror magneto-optical trap (MOT) using the external MOT coils, and 1 X 10(5) Rb-87 atoms are transferred to U-MOT using U-shaped wire in chip and a pair of bias coils.