Effect of H2S on stress corrosion cracking and hydrogen permeation behaviour of X56 grade steel in atmospheric environment

Susceptibility to stress corrosion cracking of X56 steel and its relationship with hydrogen permeation behaviour in atmospheric environment containing H2S was investigated by hydrogen permeation tests at a slow strain rate. The results show that: the fracture strain decreases with the decrease of strain rate under the same experimental conditions; the fracture strain also decreases with the increase of H2S concentration under the same strain rate, and the increased concentration of H2S has no significant effect on the hydrogen permeation in the first wet, etc. dry cycle, however has lead to increased hydrogen permeation in the later cycles. The SEM images of the fractured surfaces show clear evidences of enhanced stress corrosion cracking susceptibility by H2S.

Effect of Cl- on the corrosive wear of AISI 321 stainless steel in H2SO4 solution

The effect of Cl- on the corrosive wear behaviour of AISI 321 stainless steel in H2SO4 solution was studied via the corrosive wear rate, the load bearing capacity of passive film and the relationship between pitting and corrosive wear. There is a critical load at natural potential, below which the corrosive wear rate is slightly lowered by Cl-, while above which is increased. At natural potential there are more pits at low load than that at a higher one in the wear tracks and the pits are also deeper. The load bearing capacity is lowered by Cl- at passive region and then the corrosive wear rate increased.

The effect of additives on Cu/HZSM-5 catalyst for DME synthesis

The addition of ZnO or ZrO2 into CuO/HZSM-5 was investigated for DME synthesis from syngas by using the reactive frontal chromatography method, TPR and in situ TPR. These promoters enhanced the catalytic activity of Cu/HZSM-5 and promotion with ZnO and ZrO2 produced a maximum activity, which could be explained by the improvement of the dispersion of Cu and the promotion of CuO reduction. The Cu+ species existing during the reaction have been detected, based on which a Cu-0 <-> Cu+1 redox cycle model was put forward.

The effect of oxygen on the aromatization of methane over the Mo/HZSM-5 catalyst

The aromatization of methane over a Mo/HZSM-5 catalyst was carried out in the presence of oxygen. It is shown that the addition of a small amount of oxygen is beneficial to improve the durability of the catalyst. UV-Raman spectra disclose that the carbonaceous deposits formed on the HZSM-5 are mainly polyolefinic and aromatic, while that on the Mo/HZSM-5 is mainly polyaromatic. The small amount of O-2 added may partly remove the coke deposits on the active sites and keep the catalyst as MoOxCy/HZSM-5, thus resulting in an improvement of the catalytic performance of the Mo/HZSM-5 catalyst.

The Effect of Indexing on the Complexity of Object Recognition

Many current recognition systems use constrained search to locate objects in cluttered environments. Previous formal analysis has shown that the expected amount of search is quadratic in the number of model and data features, if all the data is known to come from a sinlge object, but is exponential when spurious data is included. If one can group the data into subsets likely to have come from a single object, then terminating the search once a "good enough" interpretation is found reduces the expected search to cubic. Without successful grouping, terminated search is still exponential. These results apply to finding instances of a known object in the data. In this paper, we turn to the problem of selecting models from a library, and examine the combinatorics of determining that a candidate object is not present in the data. We show that the expected search is again exponential, implying that naﶥ approaches to indexing are likely to carry an expensive overhead, since an exponential amount of work is needed to week out each of the incorrect models. The analytic results are shown to be in agreement with empirical data for cluttered object recognition.

The effect of chromium on sulfur resistance of Pd/HY-Al2O3 catalysts for aromatic hydrogenation

Sulfur is a major poison to noble metal catalysts for deep aromatic hydrogenation in the petroleum refining industry. In order to study the sulfur resistance of Pd-based catalysts, a series of Pd, Cr, and PdCr catalysts supported on HY-Al2O3 were studied by NH3-TPD, pyridine-adsorption IR, TPR, IR spectra of adsorbed CO, and toluene hydrogenation in the presence of 3000 ppm sulfur as thiophene under the following conditions: 533-573 K, 4.2 MPa, and WHSV 4.0 h(-1). Cr has no influence on the acidity of the catalysts. TPR patterns and in situ IR spectra of adsorbed CO revealed a strong interaction between Cr and Pd, and the frequency shift of linear bonded CO on Pd indicates that the electron density of Pd decreases with the increase of the Cr/Pd atomic ratio. The catalytic performance of Pd, Cr, and PdCr catalysts shows that the sulfur resistance of Pd is strongly enhanced by Cr, and the activity reaches its maximum when the Cr/Pd atomic ratio equals 8. The active phase model "Pd particles decorated by Cr2O3" is postulated to explain the behavior of PdCr catalysts. (C) 2001 Academic Press.

Analysis of the effect of yoga on selective attention and mental concentration in young adults

Gemstone Team Om