氧化硅有序介孔材料MCM-41的微波水热合成及用于组装ZnO纳米粒子

与传统水热合成工艺相比,采用微波水热合成新工艺可以快速合成比表面积大、孔体积和孔径大、孔径分布范围更窄、孔洞呈六方排布的有序介孔材料MCM-41.微波水热合成工艺合成的MCM-41具有合成效率高、成功率高等特点,为此类介孔材料商业化提供了高效的技术手段.采用传统水热工艺合成MCM-41通常需要48～72 h,而采用微波水热合成技术仅需要30 min.采用X射线粉晶衍射(XRD),氮气吸附等技术手段对合成MCM-41材料的物相、比表面积、孔体积、孔径等进行了表征.采用微波水热合成MCM-41的工艺参数为:微波处理的温度120 ℃,时间30 min,微波辐射功率500 W,经过滤、洗涤、干燥、焙烧等处理后,得到的MCM-41具有六方排布的孔系,晶格常数a0=4.4nm,比表面积可达1113 m2/g,平均孔径为2.7 nm,与选用同样配方采用传统水热合成工艺合成的MCM-41的性能相当,却极大提高了合成效率.采用微波水热合成工艺,同样可以合成立方晶系的MCM-48和六方晶系的SBA-15等介孔氧化硅分子筛材料.此外,在微波合成的MCM-41中采用液相工艺成功组装了ZnO纳米粒子,并对组装在MCM-41中的纳米ZnO粒子进行了光催化降解苯酚的实验研究.     

Optimization of reactive SMB and Varicol systems

A comprehensive optimization study on a simulated moving bed reactor (SMBR) system is reported in this article for the direct synthesis of methyl tertiary butyl ether (MTBE) from tertiary butyl alcohol (TBA) and methanol. The applicability of the Varicol process, which is based on non-synchronous shift of the inlet and outlet ports, is explored for the first time for a reactive system. Multi-objective (two and three objective functions) optimization has been performed for both existing as well as design stage for SMBR and Varicol systems and their efficiencies are compared. The optimization problem involves relatively large number of decision variables; both continuous variables, such as flow rates in various sections and length of the columns and discrete variables, such as number of columns and column configuration. Pareto optimal solutions are obtained. It is observed that a five-column Varicol performs better than an equivalent five-column SMBR and its performance is nearly equal to that of a six-column SMBR in terms of purity and yield of MTBE and minimal eluent consumption. This is an important inference as it enables the reduction of fixed and operating costs while at the same time helps to achieve high purity and yield of the desired product and conversion of the limiting reactant. A state-of-the-art optimization technique, viz., non-dominated sorting genetic algorithm (NSGA), which allows handling of these complex optimization problems, is employed for this study. This is the first time that, not only the separating potential of Varicol has been extended to reaction systems, but also was optimized for multiple objectives.     

A generalist herbivore in a specialist mode Metabolic,sequestrative, and defensive consequences

Adults of a generalist herbivore, the lubber grasshopper,Romalea guttata, can be converted to functional specialists by feeding them exclusively on catnip,Nepeta cataria. No obvious adverse effects on adult development resulted from this enforced monophagy. Notwithstanding the fact thatR. guttata has had no coevolutionary relationship with this Eurasian mint, it readily sequesters compounds that are identical to or derived from the terpenoid lactones that are characteristic ofN. cataria. R. guttata appears to both biomagnify minor allelochemicals and to sequester metabolites of theNepeta terpenes in its paired defensive glands. The levels of autogenously produced phenolics are not affected by feeding onN. cataria and the defensive secretions of catnip-fed grasshoppers are more repellent to ants than those of wild-fed acridids. Metabolites of theN. cataria monoterpenes are sequestered in the defensive glands when catnip is added to the natural diet ofR. guttata. The ability of a generalist,R. guttata, to facilely bioaccumulate a potpourri of foreign allelochemicals when feeding in a specialist mode is analyzed in terms of its biochemical, physiological, and functional significance. Sequestration is examined as a response to the enteric effronteries represented by the phytochemicals that can be characteristic of the overload in a monophagous diet.     

The role of pressure on thin amorphous carbon films deposited using microwave surface wave plasma CVD

We report the effects of gas composition pressure (GCP) on the optical, structural and electrical properties of thin amorphous carbon (a-C) films grown on p-type silicon and quartz substrates by microwave surface wave plasma chemical vapor deposition (MW SWP CVD). The films, deposited at various GCPs ranging from 50 to 110 Pa, were studied by UV/VIS/NIR spectroscopy, atomic force microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy and current–voltage characteristics. The optical band gap of the a-C film was tailored to a relatively high range, 2.3–2.6 eV by manipulating GCPs from 50 to 110 Pa. Also, spin density strongly depended on the band gap of the a-C films. Raman spectra showed qualitative structured changes due to sp³/sp² carbon bonding network. The surfaces of the films are found to be very smooth and uniform (RMS roughness < 0.5 nm). The photovoltaic measurements under light illumination (AM 1.5, 100 mW/cm²) show that short-circuit current density, open-circuit voltage, fill factor and photo-conversion efficiency of the film deposited at 50 Pa were 6.4 μA/cm², 126 mV, 0.164 and 1.4 × 10^− 4% respectively.     

Optimal periodic forcing of nonlinear chemical processes for performance improvements

Unsteady-state periodic operations can improve the optimal steady-state performance of nonlinear chemical processes. To examine if the optimal periodic operation is proper and to obtain the optimal forcing functions subject to various control and state constraints it is suggested in this paper to convert the problems into a form which is suitable for constrained nonlinear programming. The adopted numerical optimization method is based on employing the control parametrization technique and is thus capable of dealing with the problem of multiple input forcings and obtaining optimal forcing functions and/or parameters while subject to general constraints. Besides, it provides information about to what extent the process performance can be improved by adopting the optimal periodic control.     

Structure and properties of nanocomposites based on poly(butylene succinate) and organically modified montmorillonite

Poly(butylene succinate) and organically modified montmorillonite nanocomposites with there different compositions were prepared via melt blending in a twin‐screw extruder. The structure of the nanocomposites was studied with X‐ray diffraction and transmission electron microscopy, which revealed the formation of intercalated nanocomposites, regardless of the silicate loading. Dynamic mechanical analysis revealed a substantial increase in the storage modulus of the nanocomposites over the entire temperature range investigated. The tensile property measurements showed a relative increase in the stiffness with a simultaneous decrease in the yield strength in comparison with that of neat poly(butylene succinate). The oxygen gas barrier property of neat poly(butylene succinate) improved after nanocomposite preparation with organically modified montmorillonite. The effect of the layered‐silicate loading on the melt‐state linear viscoelastic behavior of the intercalated nanocomposites was also investigated. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 777–785, 2006     

Glass Formation and Properties in the System Calcia-Gallia-Silica

The glass-formation region of the calcia-gallia-silica system was determined. The glasses within this region were measured to have a density of 3 to 4 g/cm³, a refractive index of 1.6 to 1.73, an Abbe number between 35 and 58, a thermal expansion coefficient of 6.5 × 10⁻⁷/°C to 11.5 × 10⁻⁷/°C, softening temperatures between 730° and 790°C, and a Vickers microhardness of 5.2 to 7.3 GPa. Crystalline phases were identified along the glass-formation boundary. Infrared transmission spectra were used to explain glass structures and their effect on glass properties. The results suggest that the role of calcia in the glass structure is similar to that for calcia in calcium aluminosilicate glasses.     

The performance of a hybrid routing intelligent algorithm in a mobile ad hoc network

End-to-end delay, power consumption, and communication cost are some of the most important metrics in a mobile ad hoc network (MANET) when routing from a source to a destination. Recent approaches using the swarm intelligence (SI) technique proved that the local interaction of several simple agents to meet a global goal has a significant impact on MANET routing. In this work, a hybrid routing intelligent algorithm that has an ant colony optimisation (ACO) algorithm and particle swarm optimisation (PSO) is used to improve the various metrics in MANET routing. The ACO algorithm uses mobile agents as ants to identify the most feasible and best path in a network. Additionally, the ACO algorithm helps to locate paths between two nodes in a network and provides input to the PSO technique, which is a metaheuristic approach in SI. The PSO finds the best solution for a particle’s position and velocity and minimises cost, power, and end-to-end delay. This hybrid routing intelligent algorithm has an improved performance when compared with the simple ACO algorithm in terms of delay, power consumption, and communication cost.     

Understanding why adult participants at the World Senior Games choose a healthy diet

Background

Identifying those seniors most likely to adopt a healthy diet, the relative importance they place on certain perceived benefits associated with a healthy diet, and whether these perceived benefits are associated with selected demographic, lifestyle, and health history variables is important for directing effective dietary health promotion programs.

Methods

Analyses are based on a cross-sectional convenience sample of 670 seniors aged 50 years and older at the 2002 World Senior Games in St. George, Utah. Data are assessed using frequencies, bivariate analysis, analysis of variance, and multiple logistic regression analysis.

Results

Fruit and vegetable consumption was significantly higher in individuals aged 70–79, in women, in those not overweight or obese, and in those with excellent overall health. Dietary fiber consumption was significantly higher in former or never smokers, current and previous alcohol drinkers, in those not overweight or obese, and in those with excellent health. The strongest motivating factors identified for adopting a healthy diet were to improve the quality of life, to increase longevity, and to prevent disease. Of intermediate importance were the need to feel a sense of control and to satisfy likes or dislikes. Least important were the desire to experience a higher level of spirituality, social reasons, and peer acceptance.

Conclusion

Seniors who have adopted a healthy diet are more likely to have chosen that behavior because of perceived health benefits than for personal and social benefits. Overweight or obese individuals and those in poor health were less likely to be engaged in healthy eating behavior and require special attention by dieticians and public health professionals.

     

An industrial study of applying input space partitioning to test financial calculation engines

This paper presents results from an industrial study that applied input space partitioning and semi-automated requirements modeling to large-scale industrial software, specifically financial calculation engines. Calculation engines are used in financial service applications such as banking, mortgage, insurance, and trading to compute complex, multi-conditional formulas to make high risk financial decisions. They form the heart of financial applications, and can cause severe economic harm if incorrect. Controllability and observability of these calculation engines are low, so robust and sophisticated test methods are needed to ensure the results are valid. However, the industry norm is to use pure human-based, requirements-driven test design, usually with very little automation. The Federal Home Loan Mortgage Corporation (FHLMC), commonly known as Freddie Mac, concerned that these test design techniques may lead to ineffective and inefficient testing, partnered with a university to use high quality, sophisticated test design on several ongoing projects. The goal was to determine if such test design can be cost-effective on this type of critical software. In this study, input space partitioning, along with automation, were applied with the help of several special-purpose tools to validate the effectiveness of input space partitioning. Results showed that these techniques were far more effective (finding more software faults) and more efficient (requiring fewer tests and less labor), and the managers reported that the testing cycle was reduced from five human days to 0.5. This study convinced upper management to begin infusing this approach into other software development projects.