Effects of brief milling and acid treatment on two ordered and disordered kaolinite structures

The structural characteristics of well-ordered kaolinite (K1) and poorly ordered kaolinite (K2) after the ¼ h milling procedures, continuing acid activation with 2 M hydrochloric acid and intercalation ability with urea were assessed. Kaolinite samples were examined by X-ray powder diffraction, thermogravimetry, infrared spectroscopy analysis and specific surface area measurement. Kaolinite K1 contained a slightly higher portion of particles <2 μm (38 vol.%) than K2 (31 vol.%) increasing after jet milling (to 92 vol.% and 54 vol.%, respectively), but decreasing slightly after ball milling (to the 37 vol.% and 26 vol.%, respectively). The acid treatment contributed to a narrower particle size distribution, increased value of the surface area and dehydroxylation temperature and improved the structural order of poorly ordered kaolinites. Maximum surface area SSA = 45 m²g^{− 1} was measured for K2 after ball milling and treatment with hydrochloric acid. Treatment of kaolinites with hydrochloric acid supports their ability to intercalate urea and exfoliate, while the mechanical millings adversely affected intercalation urea. The SSA 9.8 and 20.5 m²g^{− 1} of K1 and K2, respectively, changed after: (1) exfoliation to 21.0 and 34.1 m²g^{− 1}, respectively, (2) jet milling and exfoliation to 38.0 and 42.0 m²g^{− 1}, respectively, (3) ball milling and exfoliation to 20.3 and 34.4 m²g^{− 1}, respectively, and (4) ball milling, acid treatment and exfoliation to 40.3 and 46.7 m²g^{− 1}, respectively.     

分数阶Chen混沌系统同步及Multisim电路仿真

本文针对参数已知和未知的分数阶Chen混沌系统,研究其同步控制问题。利用分数阶系统稳定性理论,设计并实现了系统的反馈控制器;同时运用Multisim软件设计实现了分数阶系统同步的混沌电路,验证了所提出同步方法的有效性和可实现性。     

Second-order data obtained from differential pulse voltammetry: Determination of tryptophan at a gold nanoparticles decorated multiwalled carbon nanotube modified glassy carbon electrode

Three-way data obtained from different pulse heights of differential pulse voltammetry (DPV) was analyzed using multivariate curve resolution by alternating least squares (MCR-ALS) algorithm. Differential pulse voltammograms of tryptophan were recorded at a gold nanoparticles decorated multiwalled carbon nanotube modified glassy carbon electrode (GCE/MWCNTs-nanoAu). The determination of tryptophan was performed even in the presence of unexpected electroactive interference(s). Both the simulated and experimental data were non-bilinear. Therefore a potential shift algorithm was used to correct the observed shift in the data. After correction, the data was augmented and MCR-ALS was applied to the augmented data. A relative error of prediction of less than 8% for the determination of the simulated analyte of interest and tryptophan in synthetic samples indicated that the methodology employing voltammetry and second-order calibration could be applied to complex analytical systems.     

An inequality for the empirical D.F. in the non–I.I.D. case

A generalization to the non-i.i.d. case of an inequality for the empirical df. due to Mason (1981) is proved     

On asymptotically Risk-effivient sequential versions of generalized U-statistics

Sequential point estimation of means of generalized U-statistics is considered. Based on a well defined stopping rule, the proposed sequential (estimation) procedure is shown to be asymptotically (first order) risk-efficient. Asymptotic distributions of sequential generalized U-statistics and the allied stopping times are also studied.     

The influence of structure order on the kinetics of dehydroxylation of kaolinite

The structural order of kaolinite is an important factor that shows a substantial effect on the processes which take place during the thermal treatment of kaolin. The influence of structural order on the dehydroxylation process was investigated by simultaneous thermogravimetry and differential thermal analysis (TG-DTA). The thermal analysis was performed on the samples with gradually decreasing structural order prepared by milling procedure. The apparent activation energy of dehydroxylation process decreases with decreasing structural order according to the exponential function. The extrapolation of experimental data leads to the estimation of apparent activation energy of 76.6 kJ mol^?1 and of frequency factor of 0.12 × 10⁴ s^?1 related to completely disordered form of kaolinite, while the ordered form shows the apparent activation energy of 216.17 kJ mol^?1 and the frequency factor of 9.26 × 10⁴ s^?1. The relationships between features such as the infrared pattern of treated material, the degree of structural order and the apparent activation energy were established.     

水轮机水门非线性控制器设计

针对水轮发电机组水门调节的刚性水锤非线性模型，采用二阶扩张状态观测器进行动态反馈线性化，并设计了相应的预期动力学方程。然后基于弹性水锤模型进行仿真实验，并与精确反馈线性化方法比较。结果显示，在三相短路故障、负荷扰动的暂态过程中两种方法动态品质相近，而动态反馈线性化方法在参数变化上具有较强的鲁棒性。     

Modeling of an oxygen-staged membrane wall gasifier: effects of secondary oxygen

A new type of entrained flow gasifier with membrane wall and two-stage oxygen supply is being developed in China. The fraction of the secondary oxygen in total oxygen (FSO) is an important parameter for this kind of gasifier. A dynamic reduced order model (ROM) based on a reactor network model (RNM) is developed for this gasifier, which is used to investigate the effects of FSO on the slag layer thickness profile on the wall and explore the potential of FSO in dynamic slag control. The ROM adopts a flexible RNM blocking method, which varies with FSO to account for the influence of FSO on the flow pattern in the gasifier. Available industrial data was used to validate the model and a detailed sensitivity analysis for the calculation of slag layer thickness was performed. Static analyses show that FSO has a marked effect on the slag thickness distribution and higher FSO leads to lower heat loss through the wall. Finally, a slag control system, which introduced FSO as an auxiliary regulator, is proposed. Dynamic simulation shows that the new control system offers an improved performance in slag control and can broaden the regulating range of operating temperature.     

Substituent effects on thermal and photo‐alignment behavior of poly(ethylene imine)s carrying azobenzene side groups

A new class of liquid‐crystalline poly(ethylene imine)s (PEIs) having four differently substituted (? CN,? C₄H₉,? OCH₃ and? NO₂) azobenzene side‐chain groups attached through alkyl spacer groups were successfully synthesized using a solution polycondensation reaction. The synthesized polymers were characterized using differential scanning calorimetry, polarized optical microscopy and X‐ray diffraction. The photochemical, thermo‐optical and photo‐orientational behavior of the polymers were investigated in detail. Spin‐coated films of PEIs with azobenzene groups having? C₄H₉,? OCH₃ and? NO₂ substituents showed out‐of‐plane molecular orientation on annealing. Except for the PEI with an azobenzene group having ? NO₂ substituent, all polymers exhibited good photoresponsive properties upon irradiation with UV and visible light. Films of PEIs with azobenzene side groups having? CN,? C₄H₉ and? OCH₃ substituents showed reversible alignment behavior from random state to out‐of‐plane and from out‐of‐plane to random state on annealing and on irradiation with UV and non‐polarized visible light. The reversibility of the molecular orientation of PEIs from random state to out‐of‐plane and from out‐of‐plane to random state greatly depended on the substituent attached to the azobenzene side‐chain group. Copyright © 2010 Society of Chemical Industry     

一种基于干扰重构的自适应干扰对消算法

从干扰信号的波束域和时域特征入手,建立了基于四阶累积量联合对角化的干扰估计模型,提出了联合干扰重构和自适应对消的主瓣干扰抑制算法,给出了处理流程和工程应用条件,分析了干扰重构的相对误差,对信噪比损失性能进行了仿真分析,同时评估了对测角性能的影响。仿真结果表明,在干噪比大于40 dB、干扰与目标夹角大于1/8 波束宽度的条件下,该算法可有效抑制主瓣干扰,其重构的干扰信号与真实干扰信号相对误差小于2% ,干扰抑制后目标回波信噪比损失小于3 dB,测角精度恶化小于波束宽度的1/30。