The Gas Phase Oxidation of Acetaldehyde Reaction Mechanism and Kinetics
K.
Hessam
Chemical & Petroleum Engineering, Imperial College of Science and Technology
author
text
article
1995
eng
The mechanism of the low temperature oxidation of gaseous acetaldehyde was investigated in the temperature range of 1 50-400?°C. The minor, intermediate and major products were identified and measured quantitatively by sampling directly into the ionization chamber of an MS10-C2 mass spectrometer from the reactor. The formation of H2O, CO, CO2, HCOOH, H2, HCHO, CH3COOH and CH3OH as the major products, the presence of H2O2, (CH3)2C0, (CH3CO)2O2, (CH3CO)2 and CH4 as the minor products, the production of the unstable product CH3OOH and the existence of peracetic acid as a degenerate branching intermediate were confirmed. The exprimental results led to a proposed degenrate branched chain mechanism for the gas-phase oxidation of acetaldehyde. This paper attempts to explain the kinetics in the region of lower slow combustion (at 150?°C), cool flames, and upper slow combustion (at 400?°C) with an initial total pressure between 4 to 12 cm., Hg. The major products detected were (in order of concentrations): H2O > CO > CO2 > H2 > CH3COOH > HCHO > HCOOH The reaction orders obtained were 0.38 with respect to oxygen pressure and 1.85 with respect to acetadehyde pressure for maximum rate. The reaction rate was found to be independent of the total pressure. In temperature range of 1 50-250?°C, the reaction was accompanied by a pressure decrease, while in 275-400?°C, a pressure increase was observed. The low activation energies of 53.50 KJ mole-1 (in 150-250?°C region) and 57 KJ mole-1. (in 275-400?°C region) indicate that the reaction is a degenerate branching chain type for which the net-branching factor is correlated with the acetaldehyde pressure and the activation energy as f = K [PCH3CHO]0.8exp[-E/RT]. The kinetics data obtained by the mass spectrometer were analyzed by computer programing and the results were presented by the appropriate kinetics plots.
International Journal of Engineering
Materials and Energy Research Center
1025-2495
8
v.
1
no.
1995
1
22
https://www.ije.ir/article_71116_cc5a42319b5062b66ec9869b564ff6a1.pdf
Robot Motion Vision Pait I: Theory
M.A.
Taalebinezhaad
MIT Artificial Intelligence Laboratory, University of Cambridge
author
text
article
1995
eng
A direct method called fixation is introduced for solving the general motion vision problem, arbitrary motion relative to an arbitrary environment. This method results in a linear constraint equation which explicitly expresses the rotational velocity in terms of the translational velocity. The combination of this constraint equation with the Brightness-Change Constraint Equation solves the general motion vision problem. Avoiding correspondence and optical flow has been the motivation behind this direct method which uses the image brightness information such as temporal and spatial brightness gradients directly. In contrast to previous direct methods, the fixation method does not put any severe restrictions on the motion or the environment. Moreover, the fixation method neither requires tracked images as its input nor uses tracking for obtaining fixated images. Instead, it introduces a pixel shifting process to construct fixated images for any arbitrary fixation point. This is done entirely in software without any use of camera motion for tracking.
International Journal of Engineering
Materials and Energy Research Center
1025-2495
8
v.
1
no.
1995
23
36
https://www.ije.ir/article_71117_cf22336614ded19a2b53eddb26d782e3.pdf
The Influence of Machine Parameters on the Properties of Double Jersey Knitted Fabrics
A. A.
A. Jeddi
Textile Engineering, Amirkabir University of Technology
author
text
article
1995
eng
The present work is an experimental account of the way in which several machine settings, particularly cylinder knock-over and dial-height, influence fabric dimensions, course length, bending behavior and load extension of fabrics produced on a circular knitting machine. The results show that there are certain optimum settings for such variables as knock-over depth and dial-height for producing fabrics with optimum liveliness, dimensions and bending behavior. This study confirms the suggestion that due to the asymmetry of fabric take-down on circular double jersey machines, it is not possible to produce a fabric with identical properties on the face and back sides. No conclusive evidence of robbing yam from the cylinder loops to dial loops which cause asymmetry in the fabrics could be found but alternate suggestions were examined.
International Journal of Engineering
Materials and Energy Research Center
1025-2495
8
v.
1
no.
1995
37
48
https://www.ije.ir/article_71118_392f7c80422f40359965cb3318bdea4e.pdf
Optimum Design of Interbasin Pipe System (RESEARCH NOTES)
B. A.
Christensen
, University of Florida
author
Arash
Najafi
Chemical Engineering, Independent Researcher
author
N.
Samani
Geomatics Engineering, Shiraz University
author
text
article
1995
eng
Pipe systems are often used to transfer moderate to medium water volumes between reservoirs or from well fields to consumers. Such systems consisting of an arbitrary number of reservoirs or other types of sources and sinks are considered here. The Lagrangean optimization principle is used for the determination of all pipe diameters giving minimum total cost of the system, when the individual discharges/recharges from/to reservoirs, elevations of the water surfaces or piezometric heads of all reservoirs, and the cost of pipes per unit length are known. Both the energy loss due to friction and the local energy loss due to gates, bends, etc. are taken into consideration. Turbulent flow in the rough flow range is assumed, i.e., the wall Reynolds number is in excess of seventy. The method may also be adapted to open channel systems, tunnel systems, or combined systems.
International Journal of Engineering
Materials and Energy Research Center
1025-2495
8
v.
1
no.
1995
49
54
https://www.ije.ir/article_71119_86201f9ad71187740714a54ea25a28e4.pdf
Study of the Enhanced Precipitation of an Aluminium 6061 Alloy Reinforced by SiC Particles in the Range of β\\\" Phase Temperature (RESEARCH NOTE)
S.M.
Seyed Reihani
Materials Engineering, Sharif University of Technology
author
text
article
1995
eng
An experimental method to follow the evolution of the precipitation phenomena in the metal-matrix composites using the thermoelectric power measurements is described. It is shown that one can follow the kinetics of the precipitation during aging. The influence of the reinforcement on the precipitation kinetics is studied in case of an aluminum 6061- SiC, composite (where SiC, represents SiC particles). The precipitation kinetics are accelerated in the case of the reinforced composite with respect to the unreinforced matrix. The variation of the microhardness of the specimens is also recorded during aging.
International Journal of Engineering
Materials and Energy Research Center
1025-2495
8
v.
1
no.
1995
55
59
https://www.ije.ir/article_71120_b5f64d8752f5a79cc1e6a9687a5795ee.pdf