Deployment of a reliable 802.11e experimental setup for throughput measurements

This paper describes an experimental setup for measuring the throughput of an 802.11 network that supports Quality of Service (QoS) mechanisms, addressing some issues concerning the comparison between experimental and theoretical results. The setup is an ad hoc network in which the nodes implement the Multiband Atheros Driver for Wireless Fidelity (MADWiFi). There are three main contributions of this study. The first one describes the adjustments to the MADWiFi source code that guarantee the control of the QoS parameters in ad hoc mode. The second contribution aims to provide a practical method for verifying if the backoff generated by a given wireless card is uniformly distributed, as dictated by the 802.11 standard. This represents a key point when theoretical and experimental results must be compared, since many vendors adopt nonuniform backoff distributions in their commercial cards. As a third contribution, this paper presents a theoretical nonsaturated analysis that provides the throughput and the successful packet delay of an 802.11 network supporting QoS in presence of nonuniform backoff. The throughput derived from this analysis using a uniform backoff, which is included in the proposed model as a particular case, is compared to the measurements provided by the deployed setup. Copyright © 2010 John Wiley & Sons, Ltd.     

Effect of Carbonaceous Residues on the Blast Furnace Operation Efficiency by PC Injection

Efficiency of pulverized coal (PC) injection determines the coke rate and, consequently, the environmental effect, and depends significantly on its conversion. At high injection rates over 200 kg t_HM⁻¹, a significant part of coal residues, named char, leave the raceway. Char properties and behavior are of great importance in view of their possible consumption outside the raceway. This study continues the investigations of previous works reported in 2020, and comprises numerous laboratory, analytical tests and simulations performed at RWTH Aachen University, as well as industrial measurements. First, the article focuses on the char formation and the temperature development in the raceway while injecting PC. In addition, the effect of alkali on the char reactivity is proven. Next, the effect of injected PC on the pressure drop and permeability in different blast furnace (BF) zones is examined. Also, the char effect on liquid products and the dripping zone is studied. Hot-metal carburization, dynamic and static holdups in the dripping zone, and slag characteristics are investigated. Further available carbonaceous residues in the BF, such as coke fines and soot, are investigated to reveal their competitive consumption. Finally, a method for identification and quantification of carbon phases in BF dust is developed.