Effect of dimensionality of a crystal lattice on the properties of a localized impurity

The changes of electron density due to the presence of a localized impurity in a crystal lattice are examined in dependence on the lattice dimensionality. The Koster–Slater impurity model developed for the case of a three-dimensional simple cubic lattice has been taken as the basis of examinations. Ordinary bound states, virtual bound states, and delocalized electron states are considered in each lattice case. For the delocalized states extended in a one-dimensional lattice the amplitude of the oscillatory changes of the electron density due to the impurity perturbation does not decrease with the distance from the impurity position, whereas for a two-dimensional lattice this amplitude decreases roughly proportionally to the reciprocal value of the square root of the distance from the impurity. Let us note that a well-known amplitude characterizing the decrease of the oscillatory change of the electron density in a three-dimensional system is proportional to the reciprocal value of the third power of the distance from the impurity position. © 2000 John Wiley & Sons, Inc. Int J Quant Chem 79: 57–74, 2000     

Finite element simulations of incompressible flow past a heated/cooled sphere

This paper reports numerical simulation of the flow past a heated/cooled sphere. A Galerkin finite element method is used to solve the 3D incompressible Boussinesq equations in primitive variable form. Numerical simulations of flow around the sphere for a range of Grashof numbers and moderate Reynolds numbers, were conducted. The drag coefficient for adiabatic flow shows good agreement with standard correlations over the range of the Reynolds numbers investigated. It is shown that the drag can vary considerably with heating of the sphere and that computational fluid dynamics methods can be used to derive constitutive laws for macroscopic momentum and heat exchange in multiphase flow. © 1998 John Wiley & Sons, Ltd.     

在不均匀旋转大气中瞬时圆形轨道的人造卫星的寿命

本文用能量观点研究了人造卫星在不均匀旋转大气的阻力作用下的寿命.根据流体动力学,大气旋转角速度随高度而减小.大气密度按指数形式而减少.文中推出了卫星在上述旋转大气模型中瞬时圆形轨道上的寿命表达式,并对具体卫星的寿命做了数值估计.结果表明:在本文中所计算出的卫星寿命比前人将大气旋转同地球自转角速度一样的模型所算出的寿命要短些.     

激光剥蚀-电感耦合等离子体质谱 (ICP-MS)法测定纯钌中19种杂质元素

建立了激光剥蚀-电感耦合等离子体质谱(LA-ICP-MS)法测定纯钌中Mg、Al、Fe、Ni、Cu、Zn、Rb、Rh、Pd、Mo、Ag、Cd、Sn、Ba、Ir、Pt、Au、Pb和Si等19种杂质元素的分析方法.优化了仪器参数,给出了激光能量为60％,剥蚀孔径为110μm,扫描速率为50μm/s,脉冲频率为10 Hz,载...     

Study of multiple impurity seeding effect using SONIC integrated divertor code for JT-60SA plasma prediction

In order to study the potential impurity seeding operation regime of the future fusion devices, the first application of the integrated divertor code SONIC to the Ar + Ne mixed-impurity seeding operation of JT-60SA steady-state high-β plasma has been carried out. In the case, Ne is added to Ar-only seeding, the separatrix electron density has fell into the desired low separatrix electron density of the scenario. This is mainly because the D⁺ flow velocity towards the inner divertor has been increased by the Ne seeding. The resultant friction force transports Ar impurities towards the inner divertor region, while impurities are stagnated in the top of scrape-off layer (SOL) in the Ar-only seeding case. The higher impurity radiation power in the divertor regions and lower one in the SOL region above the X point have been obtained in mixed-impurity seeding cases, which show similar tendency as the Ar + Ne mixed-impurity seeding experiment in JT-60 U. At the core edge, Z_eff has been slightly increased and the radiation power has been decreased as the Ne seeding rate increases. The core plasma/impurity transport has been also evaluated by the TOPICS code using the impurity density at the core edge computed by the SONIC as a boundary parameter. The results show lower Z_eff and radiation power, and higher electron temperature in the core in the mixed-impurity seeding cases. Above possible contributors to the better energy confinement indicate that the mixed-impurity seeding operation might be more effective than Ar-only seeding operation.     

Turbulent Drag Reduction with an Ultra-High-Molecular-Weight Water-Soluble Polymer in Slick-Water Hydrofracking

Water-soluble polymers as drag reducers have been widely utilized in slick-water for fracturing shale oil and gas reservoirs. However, the low viscosity characteristics, high operating costs, and freshwater consumption of conventional friction reducers limit their practical use in deeper oil and gas reservoirs. Therefore, a high viscosity water-soluble friction reducer (HVFR), poly-(acrylamide-co-acrylic acid-co-2-acrylamido-2-methylpropanesulphonic acid), was synthesized via free radical polymerization in aqueous solution. The molecular weight, solubility, rheological behavior, and drag reduction performance of HVFR were thoroughly investigated. The results showed that the viscosity-average molecular weight of HVFR is 23.2 × 10⁶ g⋅mol⁻¹. The HVFR powder could be quickly dissolved in water within 240 s under 700 rpm. The storage modulus (G′) and loss modulus (G″) as well as viscosity of the solutions increased with an increase in polymer concentration. At a concentration of 1700 mg⋅L⁻¹, HVFR solution shows 67% viscosity retention rate after heating from 30 to 90 °C, and the viscosity retention rate of HVFR solution when increasing C_NaCl to 21,000 mg⋅L⁻¹ is 66%. HVFR exhibits significant drag reduction performance for both low viscosity and high viscosity. A maximum drag reduction of 80.2% is attained from HVFR at 400 mg⋅L⁻¹ with 5.0 mPa⋅s, and drag reduction of HVFR is 75.1% at 1700 mg⋅L⁻¹ with 30.2 mPa⋅s. These findings not only indicate the prospective use of HVFR in slick-water hydrofracking, but also shed light on the design of novel friction reducers utilized in the oil and gas industry.     

飞行器船尾设计对亚声速底阻影响及风洞试验验证

减小阻力尤其是底部阻力,是飞行器增加航程的重要手段,而船尾布局则是减小底部阻力的有效措施.为研究船尾修型设计在亚声速段对飞行器阻力的影响规律,对某飞行器外形开展船尾修型设计并进行数值模拟,分析了不同船尾形状和船尾角度对飞行器阻力的影响情况,并开展了风洞试验验证.结果表明,船尾修型设计可以有效减小底部阻力;船尾采用曲线过...     

硅片分凝除铁效应的研究

针对实用硅片研磨损伤层中的铁杂质玷污问题,本文探讨了Al-Fe-Si固溶体系的分凝效应,提出了一种热处理除铁的新工艺。实验样品用紫外光致荧光谱法进行了分析,并用扫描电镜X光能谱检测。结果表明,这一工艺使铁杂质含量明显下降。     

Synergy of organic dyes for KDP crystal growth

Single potassium dihydrogen phosphate (KDP) crystals were grown in a supersaturated solution containing an organic dye (sunset yellow FCF, brilliant blue FCF, and sky blue). The growth rate, morphology, and impurity dye distribution of faces, (100) and (101) in a KDP crystal were measured as dye concentration and the supersatutation of KDP were changed. Complete expressions for the effect of dye on all aspects of the growth of KDP crystals were discussed. The growth rates of (100) and (101) faces were well correlated by the empirical equation, and resulted in good estimation of the morphology. The distribution of dye in a KDP crystal was represented by the distribution model containing the minimum growth rate for coloring. The growth rate equation and distribution equation were expressed by functions of the supersaturation and dye concentration, and they could effectively provide the operational conditions with coloring the KDP crystal. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Impurity adsorption mechanism of borax for a suspension growth condition: A comparison of models and experimental data

A fluidized bed crystallizer is employed to investigate the growth and dissolution rates of MgSO₄·7H₂O from aqueous solutions in the presence of borax as impurity at 25°C. By adding 0.5, 1, 2 and 5 wt % of impurity the pH value changes from 6.7 to 7.11, while the saturation temperature shifts to 24.8, 24.4, 24 and 23.1°C, respectively. The data on crystal growth rates from aqueous solutions as a function of impurity concentration are discussed from the standpoint of Cabrera and Vermileya, and Kubota and Mullin. The value of the impurity effect, αθ_eq, determined from analysis of the data on growth kinetics was found to be in good agreement with the value obtained from direct adsorption experiments. The estimated value of the average spacing between the adjacent adsorption active sites and the average distance between the neighbouring impurity‐adsorbed sites are also reported. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)