Enhancement to IEEE 802.11 Distributed Coordination Function to Reduce Packet Retransmissions Under Imperfect Channel Conditions

In this paper, we provide an extended model for analytical analysis of IEEE 802.11 wireless local area networks under noisy wireless channel. A reservation stage is introduced in the Markov chain model to reduce unnecessary retransmissions in the case of transmission failure due to channel error. A lot of work has been carried out to enhance the performance of 802.11 distributed coordination function in the error free channel. Throughput enhancement of 802.11 medium access control protocol under error prone channel was still missing in the available literature. Through the analysis result it is shown that the proposed method significantly improves the performance of the backoff algorithm when the reservation stage is employed in the Markov chain model. The analysis result is validated by using the network simulator tool ns-2. The proposed modifications can be employed in the Markov chain model of any backoff algorithm.     

棉氨弹性添纱针织物的动态弹性性能

研究了热定型和热收缩温度对棉氨添纱针织物的动态弹性性能的影响.为了避免在研究动态弹性回复(DER)中产生的直接作用,利用动态弹性回复系数(DERR)分析在线圈横列和线圈纵行上的综合的直接动态弹性回复(DER)值.热定型温度会影响织物的DER值,但是热收缩温度却不会对其有影响.所以,对于不同组织的针织物,有必要优化其热定...     

Study of electrochemical machining characteristics of Al/SiCp composites

Non-conventional machining is increasing in importance due to some of the specific advantages which can be exploited during machining operation. Electrochemical machining (ECM) appears to be a promising technique, since in many areas of application, it offers several special advantages including higher machining rate, better precision and control, and a wider range of materials that can be machined. The present work is, therefore, initiated to investigate the influence of some predominant electrochemical process parameters such as applied voltage, electrolyte concentration, electrolyte flow rate and tool feed rate on the metal removal rate (MRR), and surface roughness (Ra) to fulfill the effective utilization of electrochemical machining of LM25 Al/10%SiC composites produced through stir casting. The contour plots are generated to study the effect of process parameters as well as their interactions. The process parameters are optimized based on Response Surface Methodology (RSM).     

Experimental Investigation and Optimization of EDM Performance Measures of MoSi2-SiC Intermetallic Ceramic Composite using RSM with Regression Equations

Silicon - Electric Discharge Machining (EDM) is a good potential composite ceramic design and manufacturing technique. It's the first study of its kind to investigate EDM on an...     

A Triangular Complementary Split Ring Resonator Based Compact Metamaterial Antenna for Multiband Operation

Wireless Personal Communications - In this paper, a triangular complementary split ring resonator (TCSRR) based compact metamaterial antenna for multiband operation is presented. TCSRR is used to...     

High Energetic High Density Materials: A BASIC Program (FCALC) for the design and selection of efficient high energetic materials containing nitro and azido groups

A program named “FCALC” has been developed in BASIC language to calculate the detonation volumes (through a factor F) for various explosives as well as for any new organic structure. The number and kind of substiments that need to be incorporated into an unsubstituted organic compound in order to achieve maximum F factor, and thus maximum detonation velocity, can also be predicted. The program calculates F factors for a user-defined set of combinations of substituents.