Abstract: To understand working features of a micro combustor,
a computer code has been developed to study combustion of
hydrogen–air mixture in a series of chambers with same shape aspect
ratio but various dimensions from millimeter to micrometer level.
The prepared algorithm and the computer code are capable of
modeling mixture effects in different fluid flows including chemical
reactions, viscous and mass diffusion effects. The effect of various
heat transfer conditions at chamber wall, e.g. adiabatic wall, with
heat loss and heat conduction within the wall, on the combustion is
analyzed. These thermal conditions have strong effects on the
combustion especially when the chamber dimension goes smaller and
the ratio of surface area to volume becomes larger.
Both factors, such as larger heat loss through the chamber wall
and smaller chamber dimension size, may lead to the thermal
quenching of micro-scale combustion. Through such systematic
numerical analysis, a proper operation space for the micro-combustor
is suggested, which may be used as the guideline for microcombustor
design. In addition, the results reported in this paper
illustrate that the numerical simulation can be one of the most
powerful and beneficial tools for the micro-combustor design,
optimization and performance analysis.
Abstract: In communication networks where communication nodes are connected with finite capacity transmission links, the packet inter-arrival times are strongly correlated with the packet length and the link capacity (or the packet service time). Such correlation affects the system performance significantly, but little attention has been paid to this issue. In this paper, we propose a mathematical framework to study the impact of the correlation between the packet service times and the packet inter-arrival times on system performance. With our mathematical model, we analyze the system performance, e.g., the unfinished work of the system, and show that the correlation affects the system performance significantly. Some numerical examples are also provided.
Abstract: In a chirp spread spectrum (CSS) system, the overlap
technique is used for increasing bit rate. More overlaps can offer
higher data throughput; however, they may cause more intersymbol
interference (ISI) at the same time, resulting in serious bit error
rate (BER) performance degradation. In this paper, we perform the
BER analysis and derive a closed form BER expression for the
overlap-based CSS system. The derived BER expression includes
the number of overlaps as a parameter, and thus, would be very
useful in determining the number of overlaps for a specified BER.
The numerical results demonstrate that the BER derived in a closed
form closely agrees with the simulated BER.
Abstract: Sensor Network are emerging as a new tool for
important application in diverse fields like military surveillance,
habitat monitoring, weather, home electrical appliances and others.
Technically, sensor network nodes are limited in respect to energy
supply, computational capacity and communication bandwidth. In
order to prolong the lifetime of the sensor nodes, designing efficient
routing protocol is very critical. In this paper, we illustrate the
existing routing protocol for wireless sensor network using data
centric approach and present performance analysis of these protocols.
The paper focuses in the performance analysis of specific protocol
namely Directed Diffusion and SPIN. This analysis reveals that the
energy usage is important features which need to be taken into
consideration while designing routing protocol for wireless sensor
network.
Abstract: Given a parallel program to be executed on a heterogeneous
computing system, the overall execution time of the program
is determined by a schedule. In this paper, we analyze the worst-case
performance of the list scheduling algorithm for scheduling tasks
of a parallel program in a mixed-machine heterogeneous computing
system such that the total execution time of the program is minimized.
We prove tight lower and upper bounds for the worst-case
performance ratio of the list scheduling algorithm. We also examine
the average-case performance of the list scheduling algorithm. Our
experimental data reveal that the average-case performance of the list
scheduling algorithm is much better than the worst-case performance
and is very close to optimal, except for large systems with large
heterogeneity. Thus, the list scheduling algorithm is very useful in
real applications.
Abstract: Tumor classification is a key area of research in the
field of bioinformatics. Microarray technology is commonly used in
the study of disease diagnosis using gene expression levels. The
main drawback of gene expression data is that it contains thousands
of genes and a very few samples. Feature selection methods are used
to select the informative genes from the microarray. These methods
considerably improve the classification accuracy. In the proposed
method, Genetic Algorithm (GA) is used for effective feature
selection. Informative genes are identified based on the T-Statistics,
Signal-to-Noise Ratio (SNR) and F-Test values. The initial candidate
solutions of GA are obtained from top-m informative genes. The
classification accuracy of k-Nearest Neighbor (kNN) method is used
as the fitness function for GA. In this work, kNN and Support Vector
Machine (SVM) are used as the classifiers. The experimental results
show that the proposed work is suitable for effective feature
selection. With the help of the selected genes, GA-kNN method
achieves 100% accuracy in 4 datasets and GA-SVM method
achieves in 5 out of 10 datasets. The GA with kNN and SVM
methods are demonstrated to be an accurate method for microarray
based tumor classification.
Abstract: To provide a better understanding of fair share policies supported by current production schedulers and their impact on scheduling performance, A relative fair share policy supported in four well-known production job schedulers is evaluated in this study. The experimental results show that fair share indeed reduces heavy-demand users from dominating the system resources. However, the detailed per-user performance analysis show that some types of users may suffer unfairness under fair share, possibly due to priority mechanisms used by the current production schedulers. These users typically are not heavy-demands users but they have mixture of jobs that do not spread out.
Abstract: The lack of any centralized infrastructure in mobile ad
hoc networks (MANET) is one of the greatest security concerns in
the deployment of wireless networks. Thus communication in
MANET functions properly only if the participating nodes cooperate
in routing without any malicious intention. However, some of the
nodes may be malicious in their behavior, by indulging in flooding
attacks on their neighbors. Some others may act malicious by
launching active security attacks like denial of service. This paper
addresses few related works done on trust evaluation and
establishment in ad hoc networks. Related works on flooding attack
prevention are reviewed. A new trust approach based on the extent of
friendship between the nodes is proposed which makes the nodes to
co-operate and prevent flooding attacks in an ad hoc environment.
The performance of the trust algorithm is tested in an ad hoc network
implementing the Ad hoc On-demand Distance Vector (AODV)
protocol.
Abstract: WiMAX and Wi-Fi are considered as the promising
broadband access solutions for wireless MAN’s and LANs,
respectively. In the recent works WiMAX is considered suitable as a
backhaul service to connect multiple dispersed Wi-Fi ‘hotspots’.
Hence a new integrated WiMAX/Wi-Fi architecture has been
proposed in literatures. In this paper the performance of an integrated
WiMAX/Wi-Fi network has been investigated by streaming a video
conference application. The difference in performance between the
two protocols is compared with respect to video conferencing. The
Heterogeneous network was simulated in the OPNET simulator.
Abstract: In the last couple of years Bluetooth has gained a large share in the market of home and personal appliances. It is now a well established technology a short range supplement to the wireless world of 802.11. The two main trends of research that have sprung from these developments are directed towards the coexistence and performance issues of Bluetooth and 802.11 as well as the co-existence in the very short range of multiple Bluetooth devices. Our work aims at thoroughly investigating different aspects of co-channel interference and effects of transmission power, distance and 802.11 interference on Bluetooth connections.
Abstract: Lately, an interest has grown greatly in the usages of
RFID in an un-presidential applications. It is shown in the adaptation
of major software companies such as Microsoft, IBM, and Oracle
the RFID capabilities in their major software products. For example
Microsoft SharePoints 2010 workflow is now fully compatible with
RFID platform. In addition, Microsoft BizTalk server is also capable
of all RFID sensors data acquisition. This will lead to applications
that required high bit rate, long range and a multimedia content in
nature. Higher frequencies of operation have been designated for
RFID tags, among them are the 2.45 and 5.8 GHz. The higher the
frequency means higher range, and higher bit rate, but the drawback
is the greater cost. In this paper we present a single layer, low
profile patch antenna operates at 5.8 GHz with pure resistive input
impedance of 50 and close to directive radiation. Also, we propose
a modification to the design in order to improve the operation band
width from 8.7 to 13.8
Abstract: This study presents the improvement of thermal
performance of heat pipe using copper nanofluid with aqueous
solution of n-Butanol. The nanofluids kept in the suspension of
conventional fluids have the potential of superior heat transfer
capability than the conventional fluids due to their improved thermal
conductivity. In this work, the copper nanofluid which has a 40 nm
size with a concentration of 100 mg/lit is kept in the suspension of
the de-ionized (DI) water and an aqueous solution of n-Butanol and
these fluids are used as a working medium in the heat pipe. The study
discusses about the effect of heat pipe inclination, type of working
fluid and heat input on the thermal efficiency and thermal resistance.
The experimental results are evaluated in terms of its performance
metrics and are compared with that of DI water.
Abstract: In this paper, an artificial neural network simulator is
employed to carry out diagnosis and prognosis on electric motor as
rotating machinery based on predictive maintenance. Vibration data
of the primary failed motor including unbalance, misalignment and
bearing fault were collected for training the neural network. Neural
network training was performed for a variety of inputs and the motor
condition was used as the expert training information. The main
purpose of applying the neural network as an expert system was to
detect the type of failure and applying preventive maintenance. The
advantage of this study is for machinery Industries by providing
appropriate maintenance that has an essential activity to keep the
production process going at all processes in the machinery industry.
Proper maintenance is pivotal in order to prevent the possible failures
in operating system and increase the availability and effectiveness of
a system by analyzing vibration monitoring and developing expert
system.
Abstract: The private theme parks are gradually surpassing
public-owned scenic areas after many years of development and have
become a mainstream choice for domestic tourists. Previous studies
show that visitors from different backgrounds differ in consumer
behavior and satisfaction factors. An understanding of visitor
satisfaction is therefore of extreme importance to operators of
privately-owned theme parks. Importance-Performance Analysis (IPA)
is used to measure consumer's potential satisfaction with services and
has become a widely used management tool for strength and weakness
analysis for brands, products, services and point of sales. As IPA has
so far not been used to evaluate the visitor satisfaction with
privately-owned theme parks, in this study the IPA method is used to
analyze visitor satisfaction with Janfusun Fancyworld (one of the most
popular private theme parks in Taiwan) and to rank visitor focus and
satisfaction on/in theme park facilities and services. Results of the
analysis provide private theme park operators with an understanding
of user or consumer demands as well as an assessment of the quality of
services currently offered.
Abstract: 'Secure routing in Mobile Ad hoc networks' and
'Internet connectivity to Mobile Ad hoc networks' have been dealt
separately in the past research. This paper proposes a light weight
solution for secure routing in integrated Mobile Ad hoc Network
(MANET)-Internet. The proposed framework ensures mutual
authentication of Mobile Node (MN), Foreign Agent (FA) and Home
Agent (HA) to avoid various attacks on global connectivity and
employs light weight hop-by-hop authentication and end-to-end
integrity to protect the network from most of the potential security
attacks. The framework also uses dynamic security monitoring
mechanism to monitor the misbehavior of internal nodes. Security
and performance analysis show that our proposed framework
achieves good security while keeping the overhead and latency
minimal.
Abstract: Employing a recently introduced unified adaptive filter
theory, we show how the performance of a large number of important
adaptive filter algorithms can be predicted within a general framework
in nonstationary environment. This approach is based on energy conservation
arguments and does not need to assume a Gaussian or white
distribution for the regressors. This general performance analysis can
be used to evaluate the mean square performance of the Least Mean
Square (LMS) algorithm, its normalized version (NLMS), the family
of Affine Projection Algorithms (APA), the Recursive Least Squares
(RLS), the Data-Reusing LMS (DR-LMS), its normalized version
(NDR-LMS), the Block Least Mean Squares (BLMS), the Block
Normalized LMS (BNLMS), the Transform Domain Adaptive Filters
(TDAF) and the Subband Adaptive Filters (SAF) in nonstationary
environment. Also, we establish the general expressions for the
steady-state excess mean square in this environment for all these
adaptive algorithms. Finally, we demonstrate through simulations that
these results are useful in predicting the adaptive filter performance.
Abstract: Improving the performance of the QCL through block diagram as well as mathematical models is the main scope of this paper. In order to enhance the performance of the underlined device, the mathematical model parameters are used in a reliable manner in such a way that the optimum behavior was achieved. These parameters play the central role in specifying the optical characteristics of the considered laser source. Moreover, it is important to have a large amount of radiated power, where increasing the amount of radiated power represents the main hopping process that can be predicted from the behavior of quantum laser devices. It was found that there is a good agreement between the calculated values from our mathematical model and those obtained with VisSim and experimental results. These demonstrate the strength of mplementation of both mathematical and block diagram models.
Abstract: Turbine blade cooling is considered as the most
effective way of maintaining high operating temperature making use
of the available materials, and turbine systems with wet compression
have a potential for future power generation because of high efficiency
and high specific power with a relatively low cost. In this paper
performance analysis of wet-compression gas turbine cycle with
turbine blade cooling is carried out. The wet compression process is
analytically modeled based on non-equilibrium droplet evaporation.
Special attention is paid for the effects of pressure ratio and water
injection ratio on the important system variables such as ratio of
coolant fluid flow, fuel consumption, thermal efficiency and specific
power. Parametric studies show that wet compression leads to
insignificant improvement in thermal efficiency but significant
enhancement of specific power in gas turbine systems with turbine
blade cooling.
Abstract: The successful implementation of Service-Oriented Architecture (SOA) is not confined to Information Technology systems and required changes of the whole enterprise. In order to adapt IT and business, the enterprise requires adequate and measurable methods. The adoption of SOA creates new problem with regard to measuring and analysis the performance. In fact the enterprise should investigate to what extent the development of services will increase the value of business. It is required for every business to measure the extent of SOA adaptation with the goals of enterprise. Moreover, precise performance metrics and their combination with the advanced evaluation methodologies as a solution should be defined. The aim of this paper is to present a systematic methodology for designing a measurement system at the technical and business levels, so that: (1) it will determine measurement metrics precisely (2) the results will be analysed by mapping identified metrics to the measurement tools.
Abstract: Virtual Assembly (VA) is one of the key technologies
in advanced manufacturing field. It is a promising application of
virtual reality in design and manufacturing field. It has drawn much
interest from industries and research institutes in the last two decades.
This paper describes a process for integrating an interactive Virtual
Reality-based assembly simulation of a digital mockup with the
CAD/CAM infrastructure. The necessary hardware and software
preconditions for the process are explained so that it can easily be
adopted by non VR experts. The article outlines how assembly
simulation can improve the CAD/CAM procedures and structures;
how CAD model preparations have to be carried out and which
virtual environment requirements have to be fulfilled. The issue of
data transfer is also explained in the paper. The other challenges and
requirements like anti-aliasing and collision detection have also been
explained. Finally, a VA simulation has been carried out for a ball
valve assembly and a car door assembly with the help of Vizard
virtual reality toolkit in a semi-immersive environment and their
performance analysis has been done on different workstations to
evaluate the importance of graphical processing unit (GPU) in the
field of VA.