Modeling transient slag-layer phenomena in the shell/mold gap in continuous casting of steel

Mold-slag friction and fracture may cause heat-transfer variations in continuous casting, which leads to steel shell temperature and stress variations, resulting in surface cracks. Analytical transient models of liquid slag flow and solid slag stress have been coupled with a finite-difference model of heat transfer in the mold, gap, and steel shell to predict transient shear stress, friction, slip, and fracture of the slag layers. The models are validated by comparing with numerical models and plant measurements of mold friction. Using reported slag-fracture strength and time-temperature-transformation (TTT) diagrams, the models are applied to study the effect of casting speed and mold-powder viscosity properties on slag-layer behavior between the oscillating mold wall and the solidifying steel shell. The study finds that liquid-slag lubrication would produce negligible stresses. A lower mold-slag consumption rate leads to high solid friction and results in solid-slag-layer fracture and movement below a critical value. Crystalline slag tends to fracture near the meniscus and glassy slag tends to fracture near the mold exit. A medium casting speed may be the safest to avoid slag fracture, due to its having the lowest critical lubrication consumption rate. The high measured friction force in operating casters could be due to three sources: an intermittent moving solid slag layer, excessive mold taper, or mold misalignment. Other symbols are defined in Table I     

Specifics of initial steam condensation and its influence on corrosion damage in turbines

Processes of corrosion cracking of the metal of turbine blades in the region of initial steam condensation are considered. Possible ways of preventing corrosion-fatigue damage to the blades are proposed.     

FHCF: A Simple and Efficient Scheduling Scheme for IEEE 802.11e Wireless LAN

The IEEE 802.11e medium access control (MAC) layer protocol is an emerging standard to support quality of service (QoS) in 802.11 wireless networks. Some recent work shows that the 802.11e hybrid coordination function (HCF) can improve significantly the QoS support in 802.11 networks. A simple HCF referenced scheduler has been proposed in the 802.11e which takes into account the QoS requirements of flows and allocates time to stations on the basis of the mean sending rate. As we show in this paper, this HCF referenced scheduling algorithm is only efficient and works well for flows with strict constant bit rate (CBR) characteristics. However, a lot of real-time applications, such as videoconferencing, have some variations in their packet sizes, sending rates or even have variable bit rate (VBR) characteristics. In this paper we propose FHCF, a simple and efficient scheduling algorithm for 802.11e that aims to be fair for both CBR and VBR flows. FHCF uses queue length estimations to tune its time allocation to mobile stations. We present analytical model evaluations and a set of simulations results, and provide performance comparisons with the 802.11e HCF referenced scheduler. Our performance study indicates that FHCF provides good fairness while supporting bandwidth and delay requirements for a large range of network loads. Pierre Ansel received a multidisciplinary in-depth scientific training in different fields such as Pure and Applied Mathematics, Physics, Mechanics, Computer Science and Economics from the Ecole Polytechnique, Palaiseau, France. Then, he joined the Ecole Nationale Superieure des Telecommunications, Paris, France in 2005 where he went further into electronics, databases, computer network security and high speed networks. He received a multidisciplinary master of sciences degree and an additional master of sciences degree in telecommunications in 2005. He did a summer internship in 2003 in INRIA, Sophia Antipolis, France where he worked on the Quality of Service in 802.11 networks at Planete Group, France. Then in 2004, he joined France Telecom R&D, Issy-les-Moulineaux, France to work on Intranet Security issues. He designed a WiFi security supervision architecture based on WiFi Intrusion Detection Sensors. He is currently a French civil servant and belongs to the French Telecommunications Corps. Qiang Ni received the B.Eng., M.Sc. and Ph.D. degrees from Hua Zhong University of Science and Technology (HUST), Wuhan City, China in 1993, 1996 and 1999 respectively. He is currently a faculty member in the Electronic and Computer Engineering Division,School of Engineering and Design, Brunel University, West London, U.K. Between 2004 and 2005 he was a Senior Researcher at the Hamilton Institute, National University of Ireland, Maynooth. From 1999 to 2001, he was a post-doctoral research fellow in the multimedia and wireless communication laboratory, HUST, China. He visited and conducted research at the wireless and networking group of Microsoft Research Asia Lab during the year of 2000. From Sept. 2001 until may 2004, he was a research staff member at the Planète group of INRIA Sophia Antipolis France. Since 2002, he has been active as a voting member at the IEEE 802.11 wireless LAN standard working group. His current research interests include communication protocol design and performance analysis for wireless networks, cross-layer optimizations, vertical handover and mobility management in mobile wireless networks, and adaptive multimedia transmission over hybrid wired/wireless networks. He has authored /co-authored over 40 international journal/conference papers, book chapters, and standard drafts in this field. He is a member of IEEE. E-mail: Qiang.Ni@ieee.org Thierry Turletti received the M.S. (1990) and the Ph.D. (1995) degrees in computer science both from the University of Nice – Sophia Antipolis, France. He has done his PhD studies in the RODEO group at INRIA Sophia Antipolis. During the year 1995–96, he was a postdoctoral fellow in the Telemedia, Networks and Systems group at LCS, MIT. He is currently a research scientist at the Planete group at INRIA Sophia Antipolis. His research interests include multimedia applications, congestion control and wireless networking. Dr. Turletti currently serves on the Editorial Board of Wireless Communications and Mobile Computing.     

Lactic acid production from dining‐hall food waste by Lactobacillus plantarum using response surface methodology

BACKGROUND: Food waste generally has a high starch content and is rich in nutritional compounds, including lipids and proteins. It therefore represents a potential renewable resource. In this study, dining‐hall food waste was used as a substrate for lactic acid production, and response surface methodology was employed to optimise the fermentation conditions. RESULTS: Lactic acid biosynthesis was significantly affected by the interaction of protease and temperature. Protease, temperature and CaCO₃ had significant linear effects on lactic acid production, while α‐amylase and yeast extract had insignificant effects. The optimal conditions were found to be an α‐amylase activity of 13.86 U g^?1 dried food waste, a protease activity of 2.12 U g^?1 dried food waste, a temperature of 29.31 °C and a CaCO₃ concentration of 62.67 g L^?1, which resulted in a maximum lactic acid concentration of 98.51 g L^?1 (88.75% yield). An increase in inoculum size would be appropriate for accelerating the depletion of initial soluble carbohydrate to enhance the efficiency of α‐amylase in dining‐hall food waste fermentation. CONCLUSION: A suitable regression model for lactic acid production was developed based on the experimental results. Dining‐hall food waste was found to be a good substrate for lactic acid fermentation with high product yield and without nutrient supplementation. Copyright © 2008 Society of Chemical Industry     

Oxidative radical generation via nitrogen dioxide dimer conversions induced by amide groups of macromolecules

The features of initiation of free radical reactions in polymers by dimers of nitrogen dioxide are considered. The conversion of planar dimers into nitrosyl nitrate in the presence of amide groups of macromolecules has been revealed. Nitrosyl nitrate initiates radical reactions in oxidative primary process of electron transfer with formation of intermediate radical cations and nitric oxide. As a result of subsequent reactions, nitrogen‐containing radicals are produced. The dimer conversion has been exhibited by estimation of the oxyaminoxyl radical yield in characteristic reaction of p‐benzoquinone with nitrogen dioxide on addition of aromatic polyamide and polyvinylpyrrolidone to reacting system. The isomerization of planar dimers is efficient in their complexes with amide groups, as confirmed by ab initio calculations. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Temperature Dependence of the Magnetic Properties of Amorphous Fe-Me-Si-B Alloys

Alloying of amorphous Fe-Me-Si-B metallic compositions with nickel and molybdenum results in a decrease in the values of saturation magnetization in fields with a magnetic intensity of 0.72 MA/m. The same alloying additions decrease the temperature of formation of new magnetic Fe₃B-type phases, which are stable up to 873 ± 5 K.     

曲流河沉积亚相的地震识别方法

本文提出利用三维地震资料相干数据分析研究曲流河沉积相的方法，其优点是在地质分析的基础上，对沉积体系有较为明显的识别特征，且在钻井较少的地区尤为实用。该方法在济阳拗陷东北部上第三系应用中取得了较为明显的效果。     

Influence of Zirconium Addition on Magnetic Properties and Temperature Coefficient for Nanocomposite Nd10Fe78.5-xCo5ZrxB6.5 Magnets

The influence of Zr addition on magnetic properties and temperature coefficient for nanocomposite Nd10Fe78.5-xCO5ZrxB6.5 (x=0~4) bonded magnets was investigated. It was found that the room-temperature magnetic properties were remarkably improved with Zr addition due to the grain refinement and increasing volume fraction of the hard magnetic phase. The optimal magnetic properties of Jr=0.689T, iHc=769.4kA·m-1 and (BH)max=84kJ·m-3 were obtained for 2.5% Zr addition. The temperature coefficient of remanence (α) increases slightly and the temperature coefficient of coercivity (β) decreases obviously with increasing Zr content for nanocomposite Nd10Fe78.5-xCo5ZrxB6.5 (x=0~4) bonded magnets.     

A new type of polymer-polymer PVC systems with surface layers converted into hydroxyethylcyclam nanofilms of the type “hard coating on soft substrate”

With the aim of classifying PVC materials in which surface layers are converted into interpenetrated network cyclam nanofilms among polymer-polymer systems, comparative studies of their properties were carried out with consideration for the specific conditions for the preparation of the material. The density and structures of near-surface layers, the bulk ratio of the ordered and disordered forms, the dynamics of swelling in water, and the effective partial volume occupied by water molecules were studied for PVC plates prior to and after hydrothermal treatment. The conversion of the surface layers changes the structural self-organization of PVC: the polymer structure becomes more compact and ordered both in the area adjacent to the nanofilm and in the polymer bulk, which is characteristic of systems of the type “hard coating on soft substrate”. Original Russian Text ? A.Ya. Fridman, E.M. Morozova, A.Yu. Tsivadze, N.P. Sokolova, I.I. Bardyshev, A.M. Gorbunov, O.P. Shapokhina, 2007, published in Zashchita Metallov, 2007, Vol. 43, No. 5, pp. 498–502.     

Mathematical simulation of the viscous properties of concentrated suspensions

A mathematical model for calculating the viscous properties of concentrated suspensions characterized by particle sizes of 30 to 800 µm), solids volume fractions of 1 to 70 vol %, different particle-size distributions, and a shear-rate range of 0.16 to 437 s^?1, which can describe the time evolution of the properties, is proposed. The model can be applied to calculating the viscous properties of catalyst oxide pastes, particulate-filled polymeric pastes, and the like.