Steering in computational science: Mesoscale modelling and simulation

This paper outlines the benefits of computational steering for high performance computing applications. Lattice-Boltzmann mesoscale fluid simulations of binary and ternary amphiphilic fluids in two and three dimensions are used to illustrate the substantial improvements which computational steering offers in terms of resource efficiency and time to discover new physics. We discuss details of our current steering implementations and describe their future outlook with the advent of computational grids.     

Inclined fire whirls

Air entrainment, leading to strong fire whirls, is commonly thought to be caused by the buoyant rise of the hot combustion products under the influence of gravity. We have, however, created in the laboratory steady, axisymmetric strong fire whirls with axes inclined 30° from the vertical orientation, whirls which model an inclined fire whirl, about 30 m tall, observed in California wildland near the Cleveland National Forest. The results contradict the common notion of buoyancy being significant for the structure of the whirl, implying that strong fire whirls instead are dominated by rotation only, even if their axis is vertical. The new concept of rotation-controlled fire whirls is explained by a Rossby number displacing the Froude number (or the Richardson number) in describing the phenomenon.     

Bochner's Method for Cell Complexes and Combinatorial Ricci Curvature

Abstract. In this paper we present a new notion of curvature for cell complexes. For each p , we define a p th combinatorial curvature function, which assigns a number to each p -cell of the complex. The curvature of a p -cell depends only on the relationships between the cell and its neighbors. In the case that p=1 , the curvature function appears to play the role for cell complexes that Ricci curvature plays for Riemannian manifolds. We begin by deriving a combinatorial analogue of Bochner's theorems, which demonstrate that there are topological restrictions to a space having a cell decomposition with everywhere positive curvature. Much of the rest of this paper is devoted to comparing the properties of the combinatorial Ricci curvature with those of its Riemannian avatar.     

空气中激光烧蚀Cu产生等离子体发射光谱的研究

利用Q-开关Nd:YAG激光器产生的1.06 μm、10 ns的脉冲激光聚焦在空气中的Cu靶上,观测了激光诱导的Cu等离子体发射光谱.采用不同的激光能量,分析了波长范围为440 nm到540 nm的空间分辨发射光谱.在局部热力学平衡(LTE)条件近似下,根据谱线的相对强度,得到了等离子体电子温度约在104 K以上,给出了靶面附近电子温度的空间演化规律,并探讨了N(Ⅱ)500.52 nm谱线的谱线强度和半高全宽随激光能量的变化规律.     

A variable narrow bandpass optically stimulated luminescence system for quaternary geochronology

A new optically stimulated luminescence system is devised for dating Quaternary geologic sediments. This instrument can provide any chosen wavelength between 400 and 850 nm with a bandwidth of 0.4–20.4 nm and a beam intensity adjustable between 7 and 110% of full power. The measured radiant flux at the sample position varies between 9.7 and 34.3 mW/cm², providing sufficient energy for photoluminescence studies. It is hoped that this instrument will reveal the optimal wavelengths and bandwidths for dating Quaternary waterlain and other poorly light-exposed sediments.     

Novel synthesis and characterization of five isomers of (C(70))(2) fullerene dimers.

The synthesis and characterization of dimers and polymers, wherein two or more cages are linked, represent an important frontier in the chemistry of fullerene derivatives. A simple and novel method that requires no special apparatus has been developed for the dimerization of [70]fullerene to (C70)2. Upon grinding [70]fullerene in a mortar and pestle in the presence of K2CO3, five structural isomers of (C70)2 have been produced. These isomers are separated from one another via high performance liquid chromatography and are characterized by 13C NMR, UV-vis-NIR absorption and mass spectroscopy.     

Aromatic polyamides. I. Synthesis and characterization of some aromatic polyamides and their model diamides

The synthesis of some wholly aromatic polyamides based on unsubstituted and chloro- and nitro-substituted diamines by low temperature solution polymerization is described. Poly(1,3-phenylene isophthalamide) and poly(chloro-2,4-phenylene isophthalamide) were selected for further investigation. To study the two polyamides on a systematic basis their model diamides were synthesized. These materials were characterized with respect to chemical structure and purity by elemental analysis, infrared (IR), and nuclear magnetic resonance (NMR) spectroscopic techniques. The usefulness of the model compounds in the interpretation of the polymer spectra is also demonstrated.