ISSN 1556-6757




Volume 2, Issue 1, 2008


Effectiveness of Energy Dissipaters Type Friction on the Reduction of the Inelastic Seismic Responses of Moment Steel Frames 

Alfredo Reyes-Salazar, Juan de Dios Garay-Morán, and Arturo López-Barraza

The effectiveness of energy dissipaters type friction on the reduction of the inelastic seismic responses of moment steel frames (MSF) is studied. The energy dissipater devices (EDD) are placed in the beamcolumn joints. The parameters of the dissipaters are modified to vary the magnitude of the friction force. The results of the study indicate that EDD based on friction of metals can significantly reduce the seismic response of MSF. The magnitude of the reduction, in terms of interstory displacements, decreases with the fundamental period of the models used, but the reduction for interstory shears is similar for all the models. Results also indicate that many plastic hinges are formed in the frame without energy dissipaters, but no plastic hinges are developed, in general, in the frames with energy dissipaters. It indicates that using energy dissipaters type friction protect the frames from significantly yielding. It is shown that the equivalent viscous damping of energy dissipaters type friction can be much larger than that existing in a bare steel frame (x» 2%). Based on these findings, design response spectra for MSF with energy dissipaters type friction can be developed for specific sites by using appropriate amounts of equivalent viscous damping.  Full Article


CDMA Technology based Reliable Wireless Mobile Communication System on a Single Chip using Cellular Automata Concept

Subir Kumar Sarkar, G. C. Manna, S. S. Singh, T. Datta, Samir kumar Sarkar, P. K. Naskar

System designers of today, in view of cutting more and more costs are using integrated circuits, which are unique to their application. In the present work, the main intention is to improve the density of integration to a new height by integrating the Individual components of a typical mobile system into a semi-custom VLSI solution. Further, several error correction techniques are incorporated in the design to get better error free, reliable and secured communication. It is expected that the inclusion of one dimensional cellular automata technique will bring attractive features in the present design and will reduce error in communication thereby making it more reliable. Full Article


A DDoS Defense Mechanism with Topology Reconfiguration
Yu Cai

In this paper, we present design and implementation of a Secure Collective Defense (SCOLD) system against DDoS attacks. The key idea of SCOLD is to follow intrusion tolerance and topology reconfiguration paradigm, and provide alternate routes via a set of proxy servers and alternate gateways when normal route is unavailable or unstable due to network failure, congestion, or DDoS attack. The BIND9 DNS server and its DNS update utilities were enhanced to support new DNS entries with indirect routing information. The indirect route was implemented by utilizing IP Tunnel. Protocol software was developed on Linux systems. Experimental results showed that SCOLD can improve network security,
availability and performance.
Full Article


A Rule-Based Fault Detection Algorithm for a Purge System of a Ventricular Assist Device
Yih-Choung Yu

A simple fault detection algorithm was designed to monitor the purge pump operation of a rotary type ventricular assist device (AB-180 Circulatory Support System [AB-180 CSS], CardiacAssist, Inc., Pittsburgh, PA, USA). This algorithm receives the fluid pressure of the purge system, calculates the pressure derivative, and then compares with the preset thresholds to detect potential abnormal conditions, such as leaking and kinking along the purge tubing, abnormal purge rate, and stoppage of the purge pump. The thresholds were identified from bench top experiments simulating the possible failure conditions in the purge system. The algorithm was then implemented in a data acquisition system and verified with different pumps and controllers. Because of its simplicity, the algorithm only takes an insignificant computation time to process the measured signal. Therefore, it can be incorporated into the existing controller without any major design change in the controller hardware. The same concept is also applicable as an alternative way to monitor an extremely low flow rate in other devices in which directly monitoring flow rate from the devices is important, but either too expensive or too difficult to implement.
Full Article

Real-time System Identification Techniques Based on Neural Networks for a Low-cost UAV

Vishwas Puttige and Sreenatha Anavatti

This paper describes system identification techniques based on neural networks for a

nonlinear, Multi-Input Multi-Output (MIMO) system such as the Unmanned Aerial Vehicle

(UAV). A novel training scheme for an online neural network model has been tested and

implemented on the UAV and the results are presented. The online model is compared

to a trained offline neural network model to bring out the merits and demerits in both of

them. To improve the performance, the online and offline models are used in combination

to form a multi-network architecture with a dynamic selection technique to choose between

the outputs of each model based on a selection criterion. The neural network models are

based on the autoregressive technique. The techniques have been developed as a part of

the autonomous UAV program carried out at our research institution. These identification

models can be developed for different stages of flight and their outputs can be optimally

chosen to aid the control process. Each of the neural models have been validated on a

Real-time Hardware In the Loop (HIL) simulation technique. Full Article


RLC Effects on Throughput in a Mobile System

Jahangir Dadkhah Chimeh, Mohammad Hakkak and Hamidreza Bakhshi

Today wireless data communication is growing rapidly. In particular, multimedia and Internet communication by wireless systems are the most popular services. Also, the architecture of wireless networks is varying to provide such services better. In this paper, we review UTRAN (UMTS Terrestrial Radio Access Network) focusing on the RLC (Radio Link Control) sub-layer, its error recovery mechanisms and transport channels when connected to Internet. Besides, we consider data flows based on the acknowledgement mode RLC, the transparent mode MAC

and simulate the effects of RLC protocol and erroneous MAC PDUs and delays, on the throughput. Finally, we evaluate the throughput versus MAC PDU retransmission times as well as the throughput efficiency versus MAC PDU retransmission times and data block lengths.

Full Article

Design and Power-Performance Optimization of A Low Leakage Serial CAM by using DTCMOS Technique and Transistor Stacks  A. Dandapat, N. N. Mojumder, D. Mukhopadhyay

The Content Addressable Memory (CAM) is a class of memory that allows access by data instead of by physical address. On a read access to a CAM, embedded into a processor cache, each word is compared in a broadcast mode, to see if it matches the requested data; thus requiring only one access. Due to their parallel pattern matching property, CAMs are gaining increasing importance over Random Access Memory (RAM) in recent years, though design complexity and power consumption continue to remain the major drawbacks. The challenge in the design of a CAM cell is to reduce leakage power in its compare circuitry without sacrificing the speed. This paper describes a novel high-performance low power design of Serial CAM

block using Dual-Threshold CMOS (DTCMOS) technique, Transmission Gates (TG), Transistor Stacks and an efficient Match Adaptive Architecture. In this design, for high speed and low power operation, we have used four separate, though not independent techniques. Replacing pass transistors by TG, including transistor stacks in the compare circuitry and assigning appropriate threshold voltages with dual threshold technique have been found to reduce the Power Delay Product (PDP) of the basic serial CAM cell by as much as up to 30%. Switching to a unique Match Adaptive Architecture further improves this Power-Performance of the CAM block significantly as compared to the conventional configuration. Full Article

An Efficient Algorithm for the Computation of Response-time Bounds for CAN Messages 
Imad Alzeer and Naji Qatanani

This paper presents an efficient computational exhaustive method that permits to calculate both upper and lower response-time bounds for CAN messages. Response-time analysis for CAN messages is relatively limited for computations of the worst case situation. It is computed assuming a maximum transmission time and critical instant releasing of messages in the CAN system. This pessimism implies the maximum interference between messages circulated on the bus. It may be correct from a hard real-time perspective when synchronous releasing, but it doesn’t give good outlook when non-common messages releasing. Hence to obtain an analysis close to the reality, the investigated temporal constraints must take into account both effects of time phasing and bit-stuffing. By using a suitable data structure, our work introduces an elegant algorithm that is able to deal with the previous effects. The obtained results for best and worst cases response-times are different from previous results obtained when assuming an optimist and a pessimist bit-stuffing length.  Full Article

Solubility of Nitrous Oxide in Amine Aqueous Solutions

Basma Yaghi and Omar Houache

The solubility of nitrous oxide (N2O) was measured in both pure water over the temperature range (5-80)°C, and in amine aqueous solutions over the temperature range (20-60)°C under atmospheric pressure. The systems studied are monoethanolamine (MEA), diethanolamine (DEA), and diisopropanolamine (DIPA) aqueous solutions. A new correlation was developed for the solubility of N2O in water, while a semi-empirical model of the excess Henry's constant was used to correlate the solubility of N2O in amine solutions. The parameters of the correlation were determined from the measured solubility data. Generally, comparisons with experimental results from the reported literature indicate that the obtained correlations are satisfactory for estimating the solubility of N2O in amine solutions, which could be used to estimate the free-gas solubility of CO2 in amines.  Full Article