High-Temperature Strength and Creep Behavior of Melt-Infiltrated SiC-Mo≤5Si3C≤1 Composites

Molybdenum carbosilicide composites (SiC-Mo_≤5Si₃C_≤1) were fabricated via the melt-infiltration process. The fracture behavior of the composites was studied from room temperature up to 1800°C in 1 atm (∼10⁵ Pa) of argon. The bend strength of the composites slightly increased at ∼1200°C, because of the brittle-ductile transition of the intermetallic phase. The composites retained ∼90% of their room-temperature strength, even at 1700°C. Compressive creep tests were performed over a temperature range of 1760°-1850°C and a stress range of 200–250 MPa. The creep rate of the SiC-Mo_≤5Si₃C_≤1 composites was approximately an order of magnitude higher than that of reaction-bonded SiC.     

局部加压铝合金的凝固变化及其数值模拟

局部加压方法是压铸中用于消除铸件厚壁处缩孔缺陷的一种新工艺.该研究通过试验模型测量局部加压过程中金属型、铸件和加压杆的温度变化曲线,分析了传热与凝固现象.结果表明,局部加压使铸件的凝固时间大为缩短,加压杆前端的温度大幅上升,而金属型的温度则无明显变化.利用变网格技术,根据加压深度通过适时修改网格文件、初始条件和边界条件的方法,模拟了铝合金在局部加压过程中的凝固变化,并与试验结果进行了对比和讨论.     

铝合金局部加压凝固及流动数值模拟的研究

局部加压方法是压铸中用于消除铸件厚壁处缩孔缺陷的一种新工艺.本研究通过实验模型测量了不同加压条件下铸件的冷却曲线,分析了局部加压引起的凝固变化.考虑局部加压引起的补缩流动,通过适时修改网格文件、初始和边界条件的方法,模拟了局部加压过程中铝合金的凝固及流动变化,并与实验结果进行了对比,二者基本吻合.     

Modeling of extraction behavior of docosahexaenoic acid ethyl ester by utilizing slug flow prepared by microreactor

The liquid–liquid extraction dynamics of an ethyl ester of docosahexaenoic acid (DHA‐Et) with silver ion was investigated. The kinetic model was derived according to the following stepwise processes: Diffusion of DHA‐Et across the organic film, complex‐formation between DHA‐Et and silver ion at the interface, and diffusion of extracted complex across the aqueous film. The kinetic parameters for the complex‐formation reaction were determined from the investigation with the stirred transfer cell. With the proposed model and determined parameters, we predicted the uptakes of DHA‐Et for the extraction system utilizing a slug flow prepared by a microchip. The calculated uptakes showed good correlation to the experimental data. The theoretical investigation suggested that the fast equilibration realized for the slug flow extraction system was due to the large specific interfacial area of the slug caused by the presence of wall film and the thin liquid film caused by the internal circulation. © 2009 American Institute of Chemical Engineers AIChE J, 2010     

Effect of Mo on corrosion behavior of Ni20Cr–xMo alloys in air with NaCl–KCl–CaCl2 vapor at 570°C

The effect of Mo on the corrosion behavior of Ni20Cr–xMo alloys in an oxidizing chlorine-containing atmosphere using air mixed with the salt-vapor mixture of NaCl–KCl–CaCl₂ at 570°C was investigated. The results revealed that the corrosion performance of the Ni20Cr alloys in the oxidizing chlorine atmosphere was improved by Mo addition of up to 3 wt%. The Mo-free alloy formed a potassium chromate during corrosion as a result of the reaction between the Cr₂O₃ scale and KCl vapor. The chromate formation increased the chlorine potential at the scale surface and induced the breakdown of the protective Cr₂O₃ scale, resulting in internal chromium chloride precipitates and a Cr-depleted zone. In contrast, the presence of Mo resulted in the formation of a NiO scale, which did not react with the salt vapors and, therefore, prevented the formation of chromates. The beneficial effect of Mo on the high-temperature chlorination of Ni–Cr alloys in salt-vapor-containing atmospheres was ascribed to the suppression of chlorine generation due to NiO scale formation.     

Binding of organic anions by synthetic supramolecular metallopores with internal Mg2+-aspartate complexes

We report that cation-selective transmembrane pores formed by synthetic p-octiphenyl beta barrels with internal aspartate residues can be transformed into anion-permeable metallopores with internal Mg(2+)-aspartate complexes. These metallopores are shown to be useful for fluorimetric sensing of a broad variety of organic anions of biological relevance such as phytate, heparin, thiamine phosphates, and adenosine triphosphate. The negligible flippase activity measurable for Mg(2+)-free pores indicates that transmembrane p-octiphenyl beta barrels do not disturb the lipid bilayer suprastructure, in other words, they form barrel-stave rather than toroidal pores.     

MRF-based texture segmentation using wavelet decomposed images

In recent textured image segmentation, Bayesian approaches capitalizing on computational efficiency of multiresolution representations have received much attention. Most of the previous researches have been based on multiresolution stochastic models which use the Gaussian pyramid image decomposition. In this paper, motivated by nonredundant directional selectivity and highly discriminative nature of the wavelet representation, we present an unsupervised textured image segmentation algorithm based on a multiscale stochastic modeling over the wavelet decomposition of image. The model, using doubly stochastic Markov random fields, captures intrascale statistical dependencies over the wavelet decomposed image and intrascale and interscale dependencies over the corresponding multiresolution region image.     

Input system for part model in CAD from coloured hand-written illustration with use of ITV

An input system for CAD is developed to construct a part model within a computer from a hand-written sketch. The sketch is drawn based on the technical illustration method. The shape of the input part is constructed by the combination of cuboids and cylinders at present. A coloured illustration is adopted for the ease of the shape recognition and for the input of the technological information.

The illustration is fed into the computer via a black and white ITV. Colours are identified referring to the brightness of the input image. The constitutive bodies, the geometric element with the technological information and the content of the technological information are recognized through image processing such as noise filtering, thinning of the contours, detection of lines and so on. The input system outputs a set of commands to the modelling system. The integrated part model which includes not only the geometrical information but also the technological information of the part is constructed by the connected modelling system CIMS/MODE.

The combination of the input system and the modelling system can support the designer to construct the detailed part model within the computer effectively. It is expected to extend the ability of the input system to identify general hand-written illustrations so that the input method will be more practical and useful.     

A novel transfection method for mammalian cells using calcium alginate microbeads

The direct transfer of genetic materials into mammalian cells is an indispensable technique. We have developed calcium alginate (CA) microbeads which can deliver plasmid DNAs and yeast artificial chromosomes into plant and yeast cells. In this paper, we demonstrate the effective transfection of mammalian cells by CA microbeads immobilizing plasmid DNAs. The transfection was performed using the pEGFP-C1 plasmid containing the cytomegalovirus (CMV) promoter and enhanced green fluorescent protein (EGFP) gene. The transient expression of EGFP was observed 24 h after transfection. The expression efficiency was maximum when the concentration of sodium alginate was 1% and the amount of plasmid DNA was increased to 100 microg. The expression efficiency of our method using CA microbeads is 2-10 times higher than that of the polyethylene glycol (PEG) method. Our results suggest that the CA microbead mediated transfection of mammalian cells effectively delivers genetic materials into mammalian suspension cells.     

Quasicrystals as cluster aggregates

Quasicrystals are solids that exhibit symmetries long thought forbidden in nature. Since their discovery in a rapidly solidified Al-Mn alloy in 1984, the central issue in the field has been to understand why they form. Are they energetically stable compounds or stabilized by entropy? In recent years, major strides have been made in determining atomic structure, largely by direct imaging using advanced electron microscopy. One system is now known to be energetically stabilized, and quasicrystals are therefore firmly established as a new physical state of matter. They represent a unique packing of atomic clusters some tens of atoms in size, with substantial localized fluctuations, referred to as phasons. Understanding phasons may in future allow their unique macroscopic properties to be tailored for useful materials applications.