scholarly journals Novel Hybrid Orthogonal Large Set Code Sequence for High Density Wireless Networks

2014 ◽  
Vol 0 (1) ◽  
Author(s):  
Nyoman Pramaita ◽  
P. L. Johnson
Keyword(s):  
Wireless Networks ◽  
High Density ◽  
Code Sequence ◽  
Large Set

Application of Crack Layer in Modeling of Slow Crack Growth in High-Density Polyethylene

2013 ◽  
Author(s):  
Haiying Zhang ◽  
Zhenwen Zhou ◽  
Alexander Chudnovsky
Keyword(s):  
Crack Growth ◽  
High Density Polyethylene ◽  
Slow Crack Growth ◽  
Growth Failure ◽  
High Density ◽  
Large Set ◽  
Layer Model ◽  
Crack Layer ◽  
Basic Parameters ◽  
Engineering Polymers

Crack layer model provides a comprehensive foundation for modeling of fracture growth, failure analysis, and lifetime prediction. During the past two decades, it has been widely applied for modeling various aspects of brittle fracture in general. This paper illustrates in details the procedure of implementation by an example of slow crack growth in a commercialized high-density polyethylene undergoing creep conditions. Firstly, we determine experimentally the basic parameters employed in constitutive equations of crack layer model such as draw ratio λ, the specific energy of transformation γtr, and drawing stress σdr, etc.. Secondly, we implement crack layer model numerically in lab-developed “Simulator”. The paper provides a paradigm for implementation of crack layer model in slow crack growth, and a blueprint for potential software development that can be used in ranking and the lifetime assessment of a large set of engineering polymers.

PERFORMANCE EVALUATION OF ADAPTIVE MEDIA ACCESS CONTROL PROTOCOLS FOR PERVASIVE WIRELESS NETWORKS

2002 ◽  
Vol 03 (03n04) ◽  
pp. 253-272 ◽  
Author(s):  
ALVIN LIM ◽  
KUI MOK
Keyword(s):  
Wireless Networks ◽  
Access Control ◽  
Multiple Access ◽  
Error Rates ◽  
High Density ◽  
Media Access Control ◽  
Slotted Aloha ◽  
Media Access ◽  
Control Protocols ◽  
Code Division Multiple

As pervasive and high-density wireless networks become increasingly common, it is critical to address the problems of intermittent disconnection, high error rate and collision that cause degradation in the performance of wireless media access control protocols, such as slotted ALOHA Time Division Multiple Access (slotted ALOHA/TDMA) and Direct Sequence Code Division Multiple Access (DS/CDMA). We propose adaptive techniques for improving performance of media access protocols through awareness of the mobile communication environment. These techniques involve detection of intermittent disconnection, high error rates, and collisions. Upon detection and notification of these conditions by snooping devices, the media access control layer adapts its operation and synchronization accordingly to reduce delay and loss of bandwidth. Results from our simulation studies show that adaptive TDMA improves performance by as much as 12 times over basic TDMA and adaptive CDMA improves by as much as 4 times over basic CDMA in wireless network with high density cells. Overall, adaptive CDMA still performs better than adaptive TDMA by about 4 times.

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