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41.
42.
Advanced technologies and modern high-production machines for underground mining of thick gently dipping coal demand strict adherence to technological discipline, reduction in operational loss and selection of optimized ventilation modes. The authors analyze ventilation schemes used in working areas in thick gently dipping seams in order to reveal influence exerted by the schemes, methods and parameters of ventilation on distribution of air loss in mined-out areas. 相似文献
43.
44.
The effect of biochar substituted for anthracite as reductant on magnetizing-roasting pyrite cinder was investigated.The key of magnetizing-roasting is the gasification reaction between reductants and CO2.Since biochar could react with CO2 more rapidly at lower temperature,the reactivity of biochar is better than that of anthracite.The gasification of biochar could produce reducing condition ofφCO/(φCO+φCO2)about 10%-20% between 700-800 ℃,which is in accord with the atmosphere and temperature of Fe2O3 reduction.So it is beneficial to the reduction of iron mineral of pyrite cinder.Compared with anthracite,biochar could decrease the roasting temperature from825 to 750 ℃ and roasting time from 20 to 15min,which shows that a better effect of magnetization could be obtained in the condition of lower temperature and shorter time.Using biochar as reductant,iron concentrate extracted from pyrite cinder as about 64%iron grade could be produced,and the recovery is over 90% under the condition of above 90% grinding particle less than 0.045 mm and magnetic intensity of 0.124-0.194 T. 相似文献
45.
The process characteristics and control strategy of a high-purity IPA reactive distillation column were investigated. A robust nominal operation was found by maintaining an excess of propylene feed to the column and recycling the unreacted propylene to the feed instead of the top stage. Stage temperature and propylene composition with one-to-one relationship with reboiler duty and propylene feed are selected as controlled variables for maintaining bottom purity and feed ratio in the presence of possible measurement bias respectively. High nonlinearity between selected input–output pair was reduced by using variable transformation. Dynamic simulations demonstrated that such a control scheme with nonlinear transformed variable was capable of providing much superior control performance than the one using natural variable. 相似文献
46.
Over tensile stress ranges giving creep lives up to 2000 hours at 373 to 463 K, the creep and creep fracture properties of
7010 are compared with results recorded for 7075 and other precipitation-hardened aluminum alloys. Using the ϕ methodology
to quantify the systematic variations in creep curve shape with changing test conditions, the behavior patterns displayed
by the different alloys are shown to depend on the extent to which precipitate coarsening causes a progressive loss of creep
strength with increasing test duration and temperature. The ϕ relationships also introduce new approaches for rationalization
and interpretation of creep data sets, based on the activation energy for lattice diffusion in the alloy matrices and the
yield stress or UTS at the creep temperatures. 相似文献
47.
P. B. Lovyrev A. I. Lavrov V. A. Babkin A. N. Aminov S. M. Melekhin Yu. P. Kazantsev P. M. Korol’kov 《Metallurgist》2006,50(3-4):152-157
Specifications require that all the welds in 12-m-diam. decomposers with a capacity of 3600 m3 be subjected to high-temperature tempering before going into service in order to alleviate the stresses from the welding
operation. Specialists at the organizations VNIIPTkhimnefteapparatury and VNIImontazhspetsstroi have proposed out-of-furnace
volumetric (complete) of the assembled decomposer with the use of special heaters. The use of this heating method has shortened
assembly operations while providing the welds with a highquality heat treatment and reducing the stresses overall (including
welding stresses, stresses from assembly of the decomposer, etc.) The technology ensures uniform heating of the housing of
the decomposer and provides for close control over the process. The experience gained in heat-treating decomposers can also
be used in the construction of other containers that come into contact with corrosive media.
__________
Translated from Metallurg, No. 3, pp. 61–64, March, 2006. 相似文献
48.
B. Schönfelder G. Gottstein L. S. Shvindlerman 《Metallurgical and Materials Transactions A》2006,37(6):1757-1771
While the motion of twist boundaries can be readily studied by atomistic simulations with molecular dynamics (MD) under the
action of an elastic driving force, the approach fails for tilt boundaries. This is due to the interaction of the elastic
stress with the grain boundary (GB) structure, which causes plastic strain by GB sliding. A novel concept, the orientation
correlated driving force, is introduced to circumvent this problem. It is shown that this concept can be successfully applied
to the study of the migration of tilt boundaries. The migration behavior of several twist and tilt GBs was investigated. The
transition from low-to high-angle boundaries can be captured, and a structural transition of tilt boundaries was found at
high temperatures, which also affected the migration behavior. The results compare well with experimental results of the motion
high-angle boundaries, but for low-angle boundaries, the agreement is poor.
This article is based on a presentation made in the “Hillert Symposium on Thermodynamics & Kinetics of Migrating Interfaces
in Steels and Other Complex Alloys,” December 2–3, 2004, organized by The Royal Institute of Technology in Stockholm, Sweden. 相似文献
49.
Observer-based estimators (OBE) were used for estimation of state variables and kinetic parameters in an anaerobic digestion (AD) process. A simplified first-order model with time-varying kinetic parameters was used to design an OBE for kinetic parameter estimation. This approach was validated on a laboratory-scale anaerobic reactor equipped with a multiwavelength fluorometer for on-line measurements of COD and VFA concentrations in the reactor effluent. The proposed estimators provide continuous adjustment of kinetic parameters and can be used for predictions of state variables between samples acquisition and during sensor failure. 相似文献
50.