No abstract

Two polymorphs of (2-carboxyethyl)(phenyl)phosphinic acid, C 9 H 11 O 4 P, crystallize in the chiral P2 1 2 1 2 1 space group with similar unit-cell parameters. They feature an essentially similar hydrogen-bonding motif but differ slightly in their detailed geometric parameters. For both polymorphs, the unequivocal location of the hydroxy H atoms together with the expected differences in the P-O bond lengths establish unequivocally that both forms contain the S isomer; the protonated phosphinic acid and carboxy O atoms serve as hydrogen-bond donors, while the second phosphinic acid O atom acts as a double hydrogen-bond acceptor and the remaining carboxy O atom is not involved in hydrogen bonding. Thus, an undulating two-dimensional supramolecular layer aggregate is formed based on an R 4 3 (20) ring unit. Such polymorphism derives from the rotation of the CC single bonds between the two hydrogen-bond-involved carboxy and phosphinic acid moieties. organic compounds Acta Cryst. (2011). C67, o195-o197 Hu et al. Two polymorphs of C 9 H 11 O 4 P o197

Double-layer cementitious plates with absorbing microwave properties were designed, based on the impedance matching theory and electromagnetic wave propagation laws. The reflectivity of cementitious composites was measured in the frequency ranges from 8 GHz to 18GHz, and the influence of silica fume on the impedance of the composites surface was studied. Meanwhile, absorbing properties of cementitious plates, which used ferrite and carbon fiber composited ferrite as microwave absorbers, were also investigated respectively. It is shown that the addition of silica fume can improve the impedance matching between the cementitious composites and free space. Compared with the single-layer structure, the reflectivity of the double-layer cementitious plates decreased around 6 dB ~ 8 dB. The maximum reflection loss of double-layer cementitious plate employing carbon fiber and ferrite reached -16.2dB, while the absorption bandwidth under – 10 dB was from 9.6 to 18 GHz.

In this paper, the effects of immersion time on the electrochemical impedance spectroscopy model of nano-sized titanium modified epoxy coating immersed in 3.5(wt.%) sodilum chloride solution has been studied using electrochemical impedance spectroscopy(EIS). Through the analysis of the spectra of the coating at different immersion times, the results showed that the spectrum was different at the different immersion times. Therefore, the equivalent electrical circuit was varied with the increasing immersion time and there were the characteristics of the powder in the equivalent electrical circuits (electrochemical impedance spectroscopy model). By the study on the evlolution of impedance model in the given system, it was found that the nano-sized powder played an important part during the electrolyte diffusing to the surface of the substrate and the electrolyte reacting with the substrate

In this paper, the hot forging behavior of Mn18Cr18N steel is studied based on the viewpoint of meso-damage. According to high temperature tensile stress - strain curve of Mn18Cr18N steel under different temperatures, the relationships of void initiation strain and fracture strain with deformation temperature are obtained. The temperature dependence of damage threshold is obtained at 950°C~1200°C for Mn18Cr18N steel by Cockcroft & Latham criterion, That is, Ci,f value increases monotonously with temperature increasing. The corresponding deformation amounts of void initiation and fracture appearing are predicted accurately by combining Cockcroft & Latham criterion with finite element analysis during hot forging of Mn18Cr18N steel, which is in good agreement with the actual production. Under these experimental conditions, once upsetting deformation amount should be controlled in 50% based on hot upsetting test and finite element simulation. These provide theoretical instruction for preventing forging cracking of Mn18Cr18N steel.