Integrated size and topology optimization of skeletal structures with exact frequency constraints

The present paper studies the integrated size and topology optimization of skeletal structures under natural frequency constraints. It is found that, unlike the conventional compliance-oriented topology optimization problems, the considered problem may be strongly singular in the sense that the corresponding feasible domain may be disconnected and the global optimal solutions are often located at the tips of some separated low dimensional sub-domains when the cross-sectional areas of the structural components are used as design variables. As in the case of stress-constrained topology optimization, this unpleasant behavior may prevent the gradient-based numerical optimization algorithms from finding the true optimal topologies. To overcome the difficulties posed by the strongly singular optima, some particular forms of area/moment of inertia-density interpolation schemes, which can restore the connectedness of the feasible domain, are proposed. Based on the proposed optimization model, the probability of finding the strongly singular optimum with gradient-based algorithms can be increased. Numerical examples demonstrate the effectiveness of the proposed approach.     

Photoelectric conversion of photosynthetic reaction center in multilayered films fabricated by layer-by-layer assembly

Multilayered protein films which contained ordered layers of photosynthetic reaction center (RC) from Rhodobacter Sphaeroides (RS601) were assembled by means of alternate electrostatic adsorption with positively charged poly(diallyldimethylammonium chloride) (PDDA). The assembly of RC was monitored by spectrometry and photocurrent measurement. Linear film growth was observed up to about 20 cycles of adsorption. For the monolayer film, the photocurrent was about 8.5 nA cm⁻². For the multilayered film, the total photocurrent was about 77 nA cm⁻² for the 24-layer RC film, while the average photocurrent increment per adsorption cycle was about 3.2 nA cm⁻². The overall light-to-electricity conversion efficiency for a 24-layer film was about eight times higher than that for the monolayer one. The effects of electrode potential and pH on the photocurrent were also measured to illustrate the light-to-electric converting mechanism.     

Zinc hydroxystannate and zinc stannate as flame‐retardant agents for flexible poly(vinyl chloride)

The flame‐retardant and smoke‐suppressant properties of inorganic tin compounds such as zinc hydroxystannate (ZHS) and zinc stannate (ZS) were investigated in a comparison with alumina trihydrate, magnesium hydroxide, and Sb₂O₃ through the limiting oxygen index test and smoke density test. The flame‐retardant mechanisms were studied through the char yield test, SEM, quantitative analysis, thermogravimetry and differential thermal analysis. The thermal degradation in air of flexible PVC treated with the above compounds was studied by thermal analysis from ambient temperature to 800°C. The results showed that tin compounds such as ZHS and ZS could be used as a highly effective flame retardant for flexible PVC, and it appears that the tin compound may exert its action in both the condensed and vapor phases, but mainly in condensed phases as a Lewis acid. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1469–1475, 2005     

Synthesis and Morphology of TiO2 Nanotube Arrays by Anodic Oxidation Using Modified Glycerol-Based Electrolytes

Titanium dioxide (TiO₂) nanotube arrays were prepared by electrochemical anodization of titanium sheets in the glycerol 176 mL/H₂O 44 mL/NH₄F 0.5 wt% electrolytes modified with H₂SO₄ and NaAc addition. The surface morphologies, average inner diameter, and the length of the nanotube arrays changed with the solution pH in the range from 5.6 to 4.0 by adding H₂SO₄. A uniform surface morphology of the nanotubes with average inner diameter of ∼80 nm and a length of ∼1000 nm was obtained when the solution pH was 5.0. The growth rates of the nanotubes were remarkably enhanced by NaAc addition in the range of 0.04–0.14 M . With NaAc addition of 0.10 M , the length of the nanotube arrays reached 4.16 μm after an 8-h anodization, increasing 3.23 μm compared with no NaAc addition. The relationship between solution pH and growth of TiO₂ nanotubes was analyzed by current–time curves, solution electrical conductivities, and scanning electron microscopy (SEM), and the role of NaAc was also discussed based on SEM and solution electrical conductivities.     

Nanocrystalline CeO2 in SBA-15: Performance of Pt/CeO2/SBA-15 Catalyst for Water-gas-shift Reaction

CeO₂ particles confined within the pores of an SBA-15 mesoporous silica host were prepared by incipient wetness impregnation (IMP) and deposition precipitation (DP) methods. The materials were characterized by XRD, N₂-adsorption and temperature programmed reduction (TPR) to evaluate the structure, texture, and redox properties. The preparation procedure had significant impact on the assembling mode of CeO₂ inside the SBA-15 mesopores. A high dispersion of CeO₂ particles was achieved via DP, whereas the dispersion of CeO₂ prepared by IMP was found to be inhomogeneous and CeO₂ partially blocked the pores. The CO conversion in the water-gas-shift reaction was enhanced over 1 wt% Pt supported on CeO₂-modified SBA-15 obtained by DP.     

CGA560增强助磨剂在水泥粉磨中的应用研究

研究了CGA560增强助磨剂在水泥粉磨中对台时产量和水泥质量的影响。试验结果表明:在磨机状况不改变的条件下,CGA560增强助磨剂的加入可提高磨机产量10%-30%;同时可有效减少过粉磨现象,优化水泥颗粒级配,提高了水泥粉磨细度及比表面积;因而使水泥强度等性能得到了明显改善和提高。     

红外热象仪对大化肥装置高压渣油气化炉的监测

介绍高压渣油气化炉炉温监测仪表红外热象仪的工作原理、组成和监测实例,并对此仪表的干扰因素ε提供了详细的去除办法。     

Oxidative dehydrogenation of ethane over Co–BaCO3 catalysts using CO2 as oxidant: effects of Co promoter

Co–BaCO₃ catalysts exhibited high catalytic performance for oxidative dehydrogenation of ethane (ODE) using CO₂ as oxidant. The maximal formation rate of C₂H₄ was 0.264 mmol · min⁻¹ · (g · cat.)⁻¹ (48.0% C₂H₆ conversion, 92.2% C₂H₄ selectivity, 44.3% C₂H₄ yield) on 7 wt% Co–BaCO₃ catalyst at 650 °C and 6000 ml. (g · cat.)⁻¹. h⁻¹. Co–BaCO₃ catalysts were comparatively characterized by XRF, N₂ isotherm adsorption-desorption, XRD, H₂-TPR and LRs. It was found that Co⁴⁺–O species were active sites on these catalysts in ODE with CO₂. The redox cycle of Co–O species played an important role on the catalytic performance of Co–BaCO₃ catalysts. On the other hand, the co-operation of BaCO₃ and BaCoO₃ was considered to be one of possible reasons for the high catalytic activity of these catalysts.     

Synthesis, isolation, spectroscopic and electrochemical characterization of some calcium-containing metallofullerenes

A few Ca-containing mono-metallofullerenes, i.e. Ca@C₇₆, Ca@C₈₈, Ca@C₉₀ (I, II), were synthesized by an improved DC arc discharge method and isolated by a multi-stage HPLC method for the first time. These isomer-separated metallofullerenes were characterized by LD-TOF MS and UV-vis-NIR spectrometry. Their HOMO-LUMO band gaps and possible molecular geometries are discussed according to the absorption spectra in this report. In addition, the cyclic and differential pulse voltammetry of Ca@C₇₆ was conducted in MeCN/C₆H₅CH₃ (1:4 v/v). The voltammograms of Ca@C₈₂ (II, III) and Ca@C₈₄ (II) were also recorded. Their electrochemical behaviors are discussed compared with those of corresponding ytterbium metallofullerenes. The features of the Ca metallofullerenes’ electronic structures are also discussed.