Investigation of the brittle-to-ductile transition of mild steel was carried out. A representative temperature T pm was defined and the transitions for the fracture toughness and the crack arrest were discovered at T pm. On the basis of the features of cleavage fracture, the criterion for cleavage microcrack propagation across the grain boundary was established. By means of a simulation of cleavage fracture behaviour of the cracked bend specimen, the variation in the resistance to the microcrack propagation with temperature was revealed, and a sharp increase in the crack resistance because of the decrease in plastic constraint and increase in the effect of microcrack blunting at temperatures above T pm was demonstrated. The implication is that the transitions at T pm are actually the expressions of a change in the crack resistance and T pm is a temperature which marks the beginning of the great increase in the crack resistance. Moreover, T pm mainly depends on the property of material if the specimen meets a certain plastic constraint and hence the T pm can be used to describe the fracture behaviour of the steel at low temperatures
A simple and reliable HPLC–UV method was developed for the simultaneous determination of two orange pigments, rubropunctatin (RPT) and monascorubrin (MSB), in red yeast rice. Alcohols were found unsuitable for the extraction of these pigments because they chemically reacted with the pigments to afford new compounds. Thus, acetonitrile/H2O was used as the mobile phase for the chromatographic separation of RPT and MSB. Under optimal conditions, good linearity was obtained over the concentration range of 0.25–50.0 μg mL−1 and 0.5–50 μg mL−1 for RPT and MSB, respectively, with a correlation coefficient (R 2) of >0.9994. The limits of detection and quantification were 0.05 and 0.15 μg mL−1, respectively, for RPT, and 0.10 and 0.30 μg mL−1, respectively, for MSB. The recoveries of RPT and MSB in red yeast rice were 91.9–101 % and 89.8–102 %, respectively, with relative standard deviations of <5.0 %. This assay was successfully used to measure the amount of RPT and MSB produced by Monascus spp. at different fermentation times.
Ketene S,S-acetals 2 react with 2-amino-1-ethanethiol to afford the substituted 2-methylenethiazolidines 3. The structure of these products as ketene N,S-acetals is confirmed by spectroscopic data. Compounds 3a-f react with esters of α,β-unsaturated acids to give thiazolo[3,2-a] pyrid-5-one derivatives 4, 6, and 7 through an electrophilic addition and cyclocondensation sequences.
In the light of the variation of fracture behavior of cracked-bending specimen with temperature; a characteristic temperature Tpm was defined for low temperature brittleness of steel. It was demonstrated that Tpm is the temperature at which the resistance to cleavage starts to sharply increase because the plastic constraint decreases and the effect of microcrack blunting increases. It was discovered that at Tpm transitions occur in both the toughness and the crack arrest property of steel. Morever, Tpm is a representative the property of a material if the test specimens meet a certain demand of plastic constraint and hence, it can be used to describe the brittleness of mild steel at low temperature
On the basis of an analysis of the micro-features of cleavage fracture of low-carbon steel, a criterion for cleavage crack propagation across a grain boundary was established and was successfully applied to analyse cleavage fracture behavior and its governing factors. The physical meaning of the cleavage characteristic stress, S co was demonstrated. The cleavage fracture stresses of the cracked specimen at different temperatures were calculated and the results were found to be in good agreement with those measured. The mismatch of the neighbouring cleavage systems results in various resolved normal stresses in the cleavage propagation process: hence, cleavage fracture depends on both mechanical aspects and on statistically various metallurgical factors
A phase unwrapping method is developed to mathematically increase the depth-of-field for the 3D optical measurement of objects with laterally discontinuous surfaces, which contain disconnected high aspect ratio regions. This method is applied for laser holographic interferometry precision measurements. The phase wrap identification at boundary pixels, masking and recovery, dynamic segmentation and phase adjustment are developed to overcome the divergence problem in phase unwrapping of laterally discontinuous surfaces. An automotive automatic transmission valve body is applied as an example to demonstrate the developed method. Experimental results demonstrate that the proposed methods can efficiently unwrap the phase to increase the depth-of-field for laterally discontinuous surfaces. Effects of segment size and width of overlapped regions on the computational efficiency are investigated
Z. Huang
P-C Wang
J. Feng
A.G. MacDiarmid
Y. Xia
G.M. Whitesides
Computer-generated patterned hydrophobic films are produced on hydrophilic glass substrates by a microcontact ldquostamprdquo printing technique. The hydrophobic pattern is produced when the silicone elastomeric stamp (ldquoinkedrdquo with C 18H 37SiCl 3) contacts the hydrophilic surface. Thin films of polypyrrole and polyaniline are deposited preferentially on the hydrophobic patterned surfaces from dilute aqueous solutions of the polymerizing monomer. Conversely, strongly adhering films of metals such as nickel are deposited selectively by an electroless process on the hydrophilic substrate surfaces. The properties of the polymers deposited on the hydrophilic and hydrophobic surfaces will be discussed as well as the application of the patterned polymer in liquid crystal displays