Magnetic behaviors and multitransition temperatures in a nanoisland

A nanoisland consists of center spin-5/2 and perimeter spin-3/2 atoms, which is described by transverse Ising model with single-ion anisotropy. Magnetic behaviors of the nanoisland are studied by the effective-field theory with correlations and the differential operator technique. The formulas of the magnetization and the phase transition of the system are given. The numerical results of the phase transition, the magnetization, the initial susceptibility and the internal energy have been discussed. Some interesting phenomena, such as a new reentrant, are found. Namely there are multitransition temperatures dependent on competition among the single-ion anisotropies, the transverse field and the interlayer coupling. These results can provide some guidance to structure design in the nanoislands.     

Structural response of stiffened plates in similitude under a turbulent boundary layer excitation

In structural dynamics, similitude laws usually deal with simple configurations as thin flat plates with point forces. Only recently, few papers have analyzed stiffened shells or stochastic pressure loads.This research activity extends the applicability of some similitude laws, developed for thin flat plates under a turbulent boundary layer load, to ribbed plates forced by the same wall pressure fluctuations.The work addresses the problem of designing a scaled experimental test-article and, successively, of re-modulating the measured data in order to get the structural response of an original (unscaled) configuration.Due to the complexity of the structural domain, the design of a scaled configuration leads to a distorted similitude. Then, a simple approach, to circumvent the distortion effects, is proposed.     

不同材料弹体超声速侵彻钢筋混凝土靶的结构破坏对比实验

设计了超声速钻地结构弹,采用203 mm口径的火炮,开展了25 kg量级弹体在1100~1300 m/s速度范围内侵彻钢筋混凝土靶的实验研究,应用数值仿真对弹体侵彻钢筋混凝土靶的过程进行了模拟计算。基于实验和仿真结果,对超声速侵彻条件下两种金属材料弹体的结构响应、质量损失等问题进行了分析。结果表明:在超声速侵彻钢筋混凝土靶的过程中,两种金属材料的弹体结构变形破坏形式主要为头部侵蚀和侧壁磨蚀,头部侵蚀量的大小与弹体壳体材料有关,高强度G50钢材料更适合用于1200 m/s速度量级的超声速侵彻环境。对出现的“径缩”现象作了初步分析,并对今后工程应用的结构弹体设计提出了指导意见。     

Hydrogenation of acetylene into ethane–ethene mixtures over modified Pd–alumina catalysts

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Alcohol-Assisted Synthesis of Sheet-Like ZSM-5 Zeolites with Controllable Aspect Ratios

Sheet-like ZSM-5 has been regarded as a promising material for catalytic applications due to its diffusion superiority. However, it still remains a challenge to obtain a desirable sheet-like morphology because of the complex synthesis process of zeolites. Here, a facile strategy for synthesizing sheet-like ZSM-5 is developed by only adding ethanol as zeolite growth modifier in the synthesis gel. It is thought that ethanol might be preferentially absorbed on the {010} surface of zeolite crystals, interact with the exposed silicon hydroxyl groups on the crystal {010} facet, and suppress the growth of b axis, resulting in the sheet-like shape. Through finely tunning synthesis parameters, sheet-like ZSM-5 crystals with thin b-axis thickness of 90 nm and different aspect ratios could be obtained. Owing to its shorter diffusion path and optimized acidity, sheet-like ZSM-5 exhibits better catalytic performance than conventional ZSM-5 in the alkylation of benzene with ethanol.     

高密度B炸药的燃烧转爆轰实验研究

采用电探针及压力传感器测试技术对密度为1.597 g/cm3的固体B炸药（TNT/RDX=40/60）的燃烧转爆轰性能进行研究。实验结果表明,在较强的约束条件下（45号钢管,内径20 mm,外径64 mm,长500 mm）,B炸药形成了DDT现象,诱导爆轰距离为295~310 mm。     

2-甲基-4,5-二硝基三唑-1-氧化物的合成及其结构表征

以乙二醛、甲基肼和盐酸羟胺为起始原料,经缩合、肟化得到中间体肟基甲腙;该中间体不经分离直接加入到硫酸铜-吡啶-水体系中,经缩合环化得到2-甲基三唑-1-氧化物(MTO);随后用混酸(硝酸+硫酸)硝化得到目标产物2-甲基-4,5-二硝基三唑-1-氧化物(DNMTO);初步探讨了环化反应的机理,研究了反应温度与时间等因素对硝化反应的影响,确定了最佳硝化反应条件.与此同时,利用红外光谱、核磁共振、质谱及元素分析等分析了中间产物和DNMTO的组成和结构.结果表明,目标产物的总收率为16%,纯度为99%;最佳硝化反应温度为100℃,最佳硝化反应时间为0.5h.     

The structure and electronic property of the smallest C20‐glycine and Gd‐encapsulated C20‐glycine derivatives with potentially biological activity

Theoretical calculations on interaction of the C₂₀ fullerene (consists solely by pentagons) with the smallest amino acid (glycine) were carried out using density‐functional theory method. The glycine molecule energetically prefers to interact with the Top‐site on the C₂₀ cage via its amino nitrogen (N) active site. The stable ordering of three active sites on glycine molecule is NH₂‐site > O‐site > OH‐site. Moreover, when the Gd atom is encapsulated to the center of C₂₀‐glycine, the cage volume obviously increase ～24.8%; and the endohedral atom induces the generation of two strong bands in the partial density of states spectra, which could cause the effect on optical properties. Additionally, it is also found that the modified C₂₀‐glycine derivative by Gd atom can reduce the thermodynamic and kinetic stabilities. It could be expected that the study may provide a theoretical reference in exploring their intrinsic feature structurally to antitumor activity. © 2012 Wiley Periodicals, Inc.     

Experimental study and thermodynamic modeling of the MgO–NiO–SiO2 system

The MgO–NiO–SiO₂ system has been studied by a combination of thermodynamic modeling and experimental measurements of phase equilibria. A complete literature review, critical evaluation and thermodynamic modeling of phase diagrams and thermodynamic properties of all oxide phases in the MgO–NiO–SiO₂ system at 1 atm total pressure are presented. To resolve the contradictions in the literature data, a new experimental investigation has been carried out over the temperature range from (1400 to 1650) °C using an equilibration and quenching technique followed by electron probe X-ray microanalysis (EPMA). Tie-lines between olivine and monoxide, olivine and proto-pyroxene, liquid and olivine and liquid and cristobalite have been measured. The whole set of experimental data, including the new experimental results and previously published data, has been taken into consideration in thermodynamic modeling of oxide phases in the MgO–NiO–SiO₂ system. The Modified Quasichemical Model has been used for the liquid phase. A simple random mixing model with a polynomial expansion of the excess Gibbs energy has been used for the monoxide solid solution. The models for olivine and proto-pyroxene were developed within the framework of the Compound Energy Formalism. The optimized model parameters reproduce all available thermodynamic and phase diagram data within experimental error limits.     

Magnetic-resonance image segmentation based on improved variable weight multi-resolution Markov random field in undecimated complex wavelet domain

To solve the problem that the magnetic resonance (MR) image has weak boundaries, large amount of information, and low signal-to-noise ratio, we propose an image segmentation method based on the multi-resolution Markov random field (MRMRF) model. The algorithm uses undecimated dual-tree complex wavelet transformation to transform the image into multiple scales. The transformed low-frequency scale histogram is used to improve the initial clustering center of the K-means algorithm, and then other cluster centers are selected according to the maximum distance rule to obtain the coarse-scale segmentation. The results are then segmented by the improved MRMRF model. In order to solve the problem of fuzzy edge segmentation caused by the gray level inhomogeneity of MR image segmentation under the MRMRF model, it is proposed to introduce variable weight parameters in the segmentation process of each scale. Furthermore, the final segmentation results are optimized. We name this algorithm the variable-weight multi-resolution Markov random field (VWMRMRF). The simulation and clinical MR image segmentation verification show that the VWMRMRF algorithm has high segmentation accuracy and robustness, and can accurately and stably achieve low signal-to-noise ratio, weak boundary MR image segmentation.