Reconfigurable Antenna for Future Wireless Communication Systems

This paper deals with the processing techniques which are known as reconfigurable antennas: these methods are foreseen to be a booster for the future high rate wireless communications, both for the benefits in terms of performance and for the capacity gains. In particular, adaptive digital signal processing can provide improved performance for the desired signal in terms of error probability or signal-to-noise ratio while the bandwidth efficiency can be increased linearly with the number of transmitting and receiving antennas. In this article, the main antenna processing techniques are reviewed and described, aiming at highlighting performance/complexity trade-offs and how they could be implemented in the future systems. The coexistence of all these different technologies in a wireless environment requires high efficiency and flexibility of the transceiver. Future transceiver implementations which are based on the Software Defined Radio technology are also reviewed and described.     

PRECIPITATION SELECTIVITY AND GROWTH OF PEROVSKITE PHASE FROM TITANIUM BEARING BLAST FURNACE SLAG

The effects of transformation of slag composition and additive agents on the morphology, the precipitation behavior, the crystal growth, and the volume fraction (VF) of perovskite (CaO·¤TiO_2) crystal in the Ti-bearing blast furnace slags were investigated. As the morphology of perovskite is dispersed in molten slags, the crystal growth mechanism of the melting of fine dendrites and the coarsening of large grains exist throughout the solidification of molten slags. With the increase of CaO and Fe_2O_3 content, VF of perovskite obviously increases. However, high basicity leads to the viscosity of slag, which results in the reduction of the average equivalent diameter (AED). The experimental results showed that the presence of the additives CaF_2 and MnO efficiently decreased the viscosity of the slags, and obviously improved the morphology of perovskite and promoted its growth.     

Species identification of dried scallop adductor muscle (yao zhu) products sold on the market

Dried scallop adductor muscle, known as yao zhu, has been ranked in the list of the eight sea treasures in Chinese cuisine, it has been commonly recommended and consumed in China over many centuries due to its delicious taste and abundant nutrition. However, the true species composition of the dried scallop adductor muscles in the trade is unclear. Indeed, it is difficult to identify the scallop species just based on their morphological characters of processed adductor muscles. In this study, 60 yao zhu products commercialized in Chinese market were analyzed in order to authenticate species. Direct sequencing and BLAST method based on a fragment of the 16S rRNA gene were carried out and results showed that 34 products (56.7%) were scallop species Argopecten irradians, and other 26 products (43.3%) were the scallop species Mizuhopecten yessoensis, indicated the yao zhu market were dominated by the both species, which were the introduced aquaculture scallop species. Moreover, a simple and fast PCR method proved to be capable of unequivocal identification between the two species. Therefore, this work facilitates the identification of yao zhu products in the market, support of food control and protection of consumers’ rights.     

Simulation of tuyere–raceway system in blast furnace

Abstract

A uniform distribution of the blast is an important prerequisite of a balanced blast furnace operation, because the blast is the main source of the hot gases that are needed to preheat, reduce and melt iron ores. The supply of hot gas from the raceways is not necessarily uniform along the furnace periphery, but depends on flow resistances encountered on the individual bustle main tuyere–raceway–raceway boundary routes. A model for this system has been developed in order to study and analyse the effects of changes in tuyere parameters and boundary conditions. Variables such as the total blast volume, blast pressure, tuyere diameter and the combustion degree of injected reductants in the tuyeres can be studied. An online version of the model has also been developed to track how the conditions on the tuyere level change with time in operating blast furnaces.     

Formation of potassium slag in olivine fluxed blast furnace pellets

Abstract

Mineralogical evaluation of olivine pellets coated with kaolinite, taken from the LKAB experimental blast furnace, shows significant reactions with potassium. Sampling has revealed strong potassium deposition in pellets in the lower shaft close to the wall, but much less deposition towards the furnace centre. Iron reduction and the deformation of the pellets were enhanced in the zone of high alkali deposition. Thin sections of pellet samples were prepared to distinguish amorphous and crystalline slag phases for a better understanding of the formation of the potassium rich slag. Olivine breaks down to various extents to form a SiO₂–FeO–MgO–K₂O glass. The kaolinite coating shows strong reaction throughout the cross-section of the lower shaft to form kalsilite (KAlSiO₄) and K₂O rich glassy slag. Studies of thin sections of the slag products were shown to be very useful in separating amorphous phases such as the K₂O rich glass from the crystalline olivine rim.     

Mixed burden softening and melting phenomena in blast furnace operation Part 2 – Mechanism of softening and melting and impact on cohesive zone

Abstract

The present work was designed to improve the current understanding of the softening and melting (SM) mechanism of ferrous materials and to identify their potential impact on the cohesive zone in the blast furnace (BF). The lump ore, direct reduced iron (DRI) and hot briquetted iron (HBI) were individually subjected to industrial trials and their results were compared with those obtained in the laboratory (SM) tests described in first part of the present paper. The difference between melting and 10% bed shrinkage temperature obtained from the results of laboratory and industrial tests was compared and it was found within 10% limits. The SM temperatures were also correlated to the basicity, gangue and flux contents of the mixed burden. The liquid slag mass fraction was computed using FactSage software and compared with the deformation of the burden bed. These results indicated presence of a small amount of liquid at temperatures close to the softening temperature of the burden suggesting that the deformation of solid phases is the primary cause for softening of the burden. The melting of the mixed burden is dependent on the melting point of DRI and melt exudation occurs close to the meltdown of the burden. The impact of ferrous burdens on the cohesive zone was predicted on the basis of experimental results which indicated DRI/HBI is an excellent blast furnace feed material to improve the productivity and decrease the coke rate in the BF.     

Numerical study of dc arc plasma and molten bath in dc electric arc furnace

Abstract

A numerical study of the arc plasma and molten bath in a dc electric arc furnace (EAF) is useful for understanding and improving the production process of the dc EAF. In the present paper, a mathematical model based on conservation equations of mass, momentum and energy along with Maxwell's equations is developed to describe the flow field and heat transfer in the arc and molten bath regions of a dc EAF simultaneously. The governing equations are solved using the PHOENICS software package. The calculated results show good agreement with those of previous studies, giving a useful insight into the factors of arc heat transfer and bath circulation.     

Determination of thermal histories of coke in blast furnace through X-ray analysis

Abstract

A study has been undertaken to identify the source of coke fines sampled from the deadman area of the blast furnace. Using measurements of the coke crystallite dimension L _C, it was established that some of the fines found in the deadman area of a blast furnace were not simply the degradation products of the lump coke in this area. The L _C was measured using standard X-ray analysis techniques. The coke fines had a higher L _C than the coke lump and therefore have experienced a higher maximum temperature than the associated coke lump. This finding has been interpreted as at least some of the coke fines found in the deadman area (lower temperature region) have been blown there from the raceway by the high velocity hot blast.     

Ejection of steel and slag droplets from gas stirred steel melts

Abstract

Liquid ejections from gas stirred melts can be classified into small film and jet droplets caused by bubble bursting and larger splashes resulting from gas channels formed at higher exiting gas velocities. In view of the conditions in ladle metallurgy, experimental investigations were carried out at moderate to low gas flowrates in an arc heated, bottom stirred 150 kg steel melting furnace and an 80 L water tank. Droplets were collected at different heights above the melt level, while gas flowrates, viscosities, surface tensions, and slag layer thickness were varied. The number of steel droplets collected decreased greatly with height (in the range 30-110 mm) and with size (in the range 0·1-1·8 mm). Calculations showed that the entrainment of droplets is strongly influenced by the velocity of upward flowing gases. While at low flowrates typical for secondary metallurgy (0·1 m s ^-1), only droplets <50 μm will be entrained, BOF (basic oxygen furnace) typical flowrates (20-50 m s ^-1) will cause particles up to 500 μm to be carried into the dust removal systems. Higher surface tensions resulted in increased droplet ejection, while higher viscosities led to a decreasing quantity of ejected melt. Slag layers led to a decrease in the ejection of steel droplets and to an increase in ejected slag but they did not completely stop steel ejection, because gas bubbles appear to entrain steel drops when they rise through the slag layer. Bubble bursting in a pure slag system caused large but few slag droplets due to the high viscosity of the slag as compared to the steel melt.     

贝尔实验室分层空时结构和空时编码

贝尔实验室分层空时结构(BLAST)和空时编码都是提高无线传输速率非常有效的方法。文章分析两种技术的基本原理,并比较其优缺点,分析其发展方向。