Cooling of roll and strip in steel rolling

Adequate cooling of the roll and strip is of considerable importance for mill designers, process engineers, and consumers. The purpose of this paper is to review recent heat-transfer research of the cooling technology in the steel-rolling process. The importance of roll and strip cooling on the thermomechanical treatment will be discussed with an assessment of the research on the corresponding heat-transfer coefficients for various cooling systems currently used. Special laboratory apparatus resembling the cooling system used in steel mills has been developed to study the major parameters that control the cooling processes. Since the heat-transfer coefficient is the most important indicator of the effectiveness of a cooling system, the coefficient under various roll-cooling conditions is experimentally studied by the special apparatus and numerically evaluated by a finite difference technique.     

Thermal behavior of steel rolling with nonconventional rolls

Many types of nonconventional rolls, including coated, sleeved, and carbide rolls, have been developed to improve roll surface strength to increase roll life. A study of the thermal behavior of the rolling process with these nonconventional rolls is presented in this article. A numerical model, previously developed for homogeneous rolls, has been modified to study the thermal response resulting from coating, sleeve, and carbide. Both cold- and hot-rolling processes under typical operating conditions are considered. First, a cold-rolling case previously considered was studied to demonstrate the validity of the modified version and then several other cases were investigated to assess the effects of using nonconventional rolls. The numerical results indicated that the effects of the coated, sleeved, and carbide rolls were favorable for increasing roll life.     

Performance of some SQP algorithms on structural design problems

This paper describes the basic ideas of sequential quadratic programming (SQP) algorithms for design optimization. There are two fundamental differences between the various algorithms: (i) the difinition of the QP subproblem solved at each iteration, and (ii) the descent function used during step size determination. The performances of the algorithms can change dramatically depending on how the two steps are executed. Numerical implementation details of various computational steps are discussed. Three programs based on SQP algorithms are used to solve 17 structural design problems having 7 to 96 design variables and 10 to 1051 performance constraints besides design variable bounds. Based on the performance of these programs, efficient procedures to execute various steps of the SQP methods are determined. It is concluded that the potential constraint strategy, where only a subset of the constraints is used to define the QP subproblem, is essential for large scale engineering design applications. With this strategy the SQP methods are quite robust and have great potential for routine application in engineering design.     

Electrical Properties of Porous Titania Ceramic Humidity Sensors

Ceramic humidity sensors made with pure TiO₂ powder as the starting material are investigated. The sensor can be reversibly operated without repeated high-temperature thermal desorption, and the conductance versus relative humidity (rh) sensitivity of the sensor is more than 4 orders of magnitude in the range ∼15% to 95% rh at 400 Hz and 25°C. The sensor can be polarized similar to electrolytes in the charging process, and the degree of polarization is enhanced with increasing rh. The conduction carriers of the sensor in the humid atmosphere are ions and electrons, and ions are the dominant conduction carrier. The relative dielectric dispersion k'(ω) is almost proportional to ω^−1.84 for rh ∼50% to 95% at low frequencies, where ω is the angular frequency. An inductive effect is also observed in a low-humidity atmosphere, which implies desorption of water vapor with the regeneration of the adsorption sites.     

Ozonation of complex industrial park wastewater: effects on the change of wastewater characteristics

BACKGROUND: Ozonation of complex industrial park wastewater was carried out in a semi‐batch reactor. The variation of wastewater characteristics was evaluated based on the analysis of 5‐day biochemical oxygen demand (BOD₅) concentration, BOD₅/chemical oxygen demand (COD) ratio, COD fractionation, and dissolved organic carbon (DOC) molecular size distribution before and after ozonation. RESULTS: The experimental results indicated that low efficiency of COD removal with increasing tendency of BOD₅ concentration generally appeared after ozonation. Also, the BOD₅/COD ratio increased from an initial of 0.27 to a maximum of 0.38. The COD fractionation tests revealed that most of the inert soluble COD was transformed to biodegradable soluble COD at 30 min of reaction time. Additionally, the DOC molecular size distribution tests showed that the fraction larger than 500 kDa was significantly decreased and the fraction smaller than 2 kDa was increased when the reaction time was prolonged to 240 min. CONCLUSION: This study verified that partial oxidation of the complex industrial park wastewater by ozonation could enhance wastewater biodegradability. The biodegradability enhancement was primarily because the inert soluble COD fraction was converted to the biodegradable soluble COD and the high molecular weight fraction of DOC was shifted toward the low molecular weight fraction. Copyright © 2009 Society of Chemical Industry     

Surface oxidation of molten Sn(Ag,Ni, In,Cu) alloys

The surface oxidations of molten Sn(Ag, Ni, In, Cu) alloys are studied. We conclude that the microstructure (phase and density) of the surface oxide layer is the key factor for the surface oxidation formation. Also, we found that the microstructure (phase and density) of the Sn surface oxide layer is highly influenced by the additives in the solder alloys, which can be roughly anticipated from the additives’ electromagnetic field values and Gibbs free energies of oxide formation. The detailed effect (either retarding or enhancing) of the additives on the surface oxidation is discussed in this paper.     

Optimal power flow by a fuzzy based hybrid particle swarm optimization approach

This paper presents a fuzzy based hybrid particle swarm optimization (PSO) approach for solving the optimal power flow (OPF) problem with uncertainties. Wind energy systems are being considered in the study power systems. OPF is an optimization problem which minimizes the total thermal unit fuel cost, total emission, and total real power loss while satisfying physical and technical constraints on the network. When performing the OPF problem in conventional methods, the load demand and wind speed must be forecasted to prevent errors. However, actually there are always errors in these forecasted values. A characteristic feature of the proposed fuzzy based hybrid PSO method is that the forecast load demand and wind speed errors can be taken into account using fuzzy sets. Fuzzy set notations in the load demand, wind speed, total fuel cost, total emission, and total real power loss are developed to obtain the optimal setting under an uncertain environment. To demonstrate the effectiveness of the proposed method, the OPF problem is performed on the IEEE 30- and 118-Bus test systems.     

Effect of silanes on the morphology,hydrophobicity, and dynamical mechanical properties of polyimide/silica hybrid membranes

Polyimide (PI)/silica hybrid membranes with high contact angles were prepared through the in situ sol–gel process. The precursor, poly(amic acid) with controlled block chain length, was synthesized using 4,4′‐diaminodiphenyl ether (ODA), 3,3′,4,4′‐benzophenone‐tetracarboxylic dianhydride (BTDA) and 3‐aminopropyl‐trimethoxysilane (APrTMOS) or 3‐aminopropyldimethylethoxysilane (APDiMOS). And then, phenyltrimethoxysilane (PTS) or tetramethoxysilane (TMOS) or methyltrimethoxysilane (MTrMOS) was respectively, added to the above polyamic acid and mixed thoroughly. Following curing reaction, the PI/silica hybrid membranes with different cross‐linkages, silica content, and hydrophobic properties were prepared. The effect on the formation of PI imide ring during imidization reaction is increased as the increase of silanes content and characterized by frequency shiftment and absorbance ratio of Fourier transform infrared (FTIR) measurements. All the hybrid membranes show high transparency though with high silica contents. The storage modulus, tan δ, and damping intensity by DMA measurements are all correlated with silane content or block chain length. And all these membranes with silane content possess high contact angle as compared to pure PI without any silanes added and the contact angles increase with increasing the silane content. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011