Abstract: The author present PID controller design for
following control of hard disk drive by characteristic ratio assignment
method. The study in this paper concerns design of a PID controller
which sufficiently robust to the disturbances and plant perturbations
on following control of hard disk drive. Characteristic Ratio
Assignment (CRA) is shown to be an efficient control technique to
serve this requirement. The controller design by CRA is based on the
choice of the coefficients of the characteristic polynomial of the
closed loop system according to the convenient performance criteria
such as equivalent time constant and ration of characteristic
coefficient. Hence, in this study, CRA method is applied in PID
controller design for following control of hard disk drive. Matlab
simulation results shown that CRA design is fairly stable and robust
whilst giving the convenience in controller-s parameters adjustment.
Abstract: The subcellular organelles called oil bodies (OBs) are lipid-filled quasi-spherical droplets produced from the endoplasmic reticulum (ER) and then released into the cytoplasm during seed development. It is believed that an OB grows by coalescence with other OBs and that its stability depends on the composition of oleosins, major proteins inserted in the hemi membrane that covers OBs. In this study, we measured the OB-volume distribution from different genotypes of A. thaliana after 7, 8, 9, 10 and 11 days of seed development. In order to test the hypothesis of OBs dynamics, we developed a simple mathematical model using non-linear differential equations inspired from the theory of coagulation. The model describes the evolution of OB-volume distribution during the first steps of seed development by taking into consideration the production of OBs, the increase of triacylglycerol volume to be stored, and the growth by coalescence of OBs. Fitted parameters values show an increase in the OB production and coalescence rates in A. thaliana oleosin mutants compared to wild type.
Abstract: In literatures, many researches proposed various
methods to reduce PAPR (Peak to Average Power Ratio). Among
those, DSI (Dummy Sequence Insertion) is one of the most attractive
methods for WiMAX systems because it does not require side
information transmitted along with user data. However, the
conventional DSI methods find dummy sequence by performing an
iterative procedure until achieving PAPR under a desired threshold.
This causes a significant delay on finding dummy sequence and also
effects to the overall performances in WiMAX systems. In this paper,
the new method based on DSI is proposed by finding dummy
sequence without the need of iterative procedure. The fast DSI
method can reduce PAPR without either delays or required side
information. The simulation results confirm that the proposed method
is able to carry out PAPR performances as similar to the other
methods without any delays. In addition, the simulations of WiMAX
system with adaptive modulations are also investigated to realize the
use of proposed methods on various fading schemes. The results
suggest the WiMAX designers to modify a new Signal to Noise Ratio
(SNR) criteria for adaptation.
Abstract: The speculative locking (SL) protocol extends the twophase locking (2PL) protocol to allow for parallelism among conflicting transactions. The adaptive speculative locking (ASL) protocol provided further enhancements and outperformed SL protocols under most conditions. Neither of these protocols consider the impact of network latency on the performance of the distributed database systems. We have studied the performance of ASL protocol taking into account the communication overhead. The results indicate that though system load can counter network latency, it can still become a bottleneck in many situations. The impact of latency on performance depends on many factors including the system resources. A flexible discrete event simulator was used as the testbed for this study.
Abstract: In this paper we study a food chain model with three trophic levels and Michaelis-Menten type ratio-dependent functional response. Distinctive feature of this model is the sensitive dependence of the dynamical behavior on the initial populations and parameters of the real world. The stability of the equilibrium points are also investigated.
Abstract: Number of breakdowns experienced by a machinery is a highly under-dispersed count random variable and its value can be attributed to the factors related to the mechanical input and output of that machinery. Analyzing such under-dispersed count observations as a function of the explanatory factors has been a challenging problem. In this paper, we aim at estimating the effects of various factors on the number of breakdowns experienced by a passenger car based on a study performed in Mauritius over a year. We remark that the number of passenger car breakdowns is highly under-dispersed. These data are therefore modelled and analyzed using Com-Poisson regression model. We use quasi-likelihood estimation approach to estimate the parameters of the model. Under-dispersion parameter is estimated to be 2.14 justifying the appropriateness of Com-Poisson distribution in modelling under-dispersed count responses recorded in this study.
Abstract: On March 11, 2011, the East coast of Japan was hit by
one of the strongest earthquakes in history, followed by a devastating
tsunami. Although most lifelines, infrastructure, and public facilities
have been restored gradually, recovery efforts in terms of disposal of
disaster waste and revival of primary industry are lagging. This study
presents a summary of the damage inflicted by the earthquake and the
current status of reconstruction in the disaster area. Moreover, we
discuss the current trends and future perspectives on recently
implemented eco-friendly reconstruction projects and focus on the
pro-environmental behavior of disaster victims which is emerging as a
result of the energy shortage after the earthquake. Finally, we offer
ideas for initiatives for the next stage of the reconstruction policies.
Abstract: Multimedia courseware has been accepted as a tool
that can support teaching and learning process. 'Li2D' courseware
was developed to assist student-s visualization on the topic of Loci in
Two Dimension. This paper describes an evaluation on the
effectiveness and usability of a 'Li2D' courseware. The quasi
experiment was used for the effectiveness evaluation. Usability
evaluation was accomplished based on four constructs of usability,
namely: efficiency, learnability, screen design and satisfaction. An
evaluation on the multimedia elements was also conducted. A total of
63 students of Form Two are involved in the study. The students are
divided into two groups: control and experimental. The experimental
group had to interact with 'Li2D' courseware as part of the learning
activities while the control group used the conventional learning
methods. The results indicate that the experimental group performed
better than the control group in understanding the Loci in Two
Dimensions topic. In terms of usability, the results showed that the
students agreed on the usability in multimedia elements in the 'Li2D'
courseware.
Abstract: With the drastically growth in optical communication
technology, a lossless, low-crosstalk and multifunction optical switch
is most desirable for large-scale photonic network. To realize such a
switch, we have introduced the new architecture of optical switch
that embedded many functions on single device. The asymmetrical
architecture of OXADM consists of 3 parts; selective port, add/drop
operation, and path routing. Selective port permits only the interest
wavelength pass through and acts as a filter. While add and drop
function can be implemented in second part of OXADM architecture.
The signals can then be re-routed to any output port or/and perform
an accumulation function which multiplex all signals onto single path
and then exit to any interest output port. This will be done by path
routing operation. The unique features offered by OXADM has
extended its application to Fiber to-the Home Technology (FTTH),
here the OXADM is used as a wavelength management element in
Optical Line Terminal (OLT). Each port is assigned specifically with
the operating wavelengths and with the dynamic routing management
to ensure no traffic combustion occurs in OLT.
Abstract: The process for predicting the ballistic properties of a liquid rocket engine is based on the quantitative estimation of idealized performance deviations. In this aim, an equilibrium chemistry procedure is firstly developed and implemented in a Fortran routine. The thermodynamic formulation allows for the calculation of the theoretical performances of a rocket thrust chamber. In a second step, a computational fluid dynamic analysis of the turbulent reactive flow within the chamber is performed using a finite volume approach. The obtained values for the “quasi-real" performances account for both turbulent mixing and chemistryturbulence coupling. In the present work, emphasis is made on the combustion efficiency performance for which deviation is mainly due to radial gradients of static temperature and mixture ratio. Numerical values of the characteristic velocity are successfully compared with results from an industry-used code. The results are also confronted with the experimental data of a laboratory-scale rocket engine.
Abstract: In this paper we have proposed a novel dynamic least cost multicast routing protocol using hybrid genetic algorithm for IP networks. Our protocol finds the multicast tree with minimum cost subject to delay, degree, and bandwidth constraints. The proposed protocol has the following features: i. Heuristic local search function has been devised and embedded with normal genetic operation to increase the speed and to get the optimized tree, ii. It is efficient to handle the dynamic situation arises due to either change in the multicast group membership or node / link failure, iii. Two different crossover and mutation probabilities have been used for maintaining the diversity of solution and quick convergence. The simulation results have shown that our proposed protocol generates dynamic multicast tree with lower cost. Results have also shown that the proposed algorithm has better convergence rate, better dynamic request success rate and less execution time than other existing algorithms. Effects of degree and delay constraints have also been analyzed for the multicast tree interns of search success rate.
Abstract: Martensitic stainless steels have been extensively used for their good corrosion resistance and better mechanical properties. Heat treatment was suggested as one of the most excellent ways to this regard; hence, it affects the microstructure, mechanical and corrosion properties of the steel. In the current research work the microstructural changes and corrosion behavior in an AISI 420A stainless steel exposed to temperatures in the 980-1035oC range were investigated. The heat treatment is carried out in vacuum furnace within the said temperature range. The quenching of the samples was carried out in oil, brine and water media. The formation and stability of passive film was studied by Open Circuit Potential, Potentiodynamic polarization and Electrochemical Scratch Tests. The Electrochemical Impedance Spectroscopy results simulated with Equivalent Electrical Circuit suggested bilayer structure of outer porous and inner barrier oxide films. The quantitative data showed thick inner barrier oxide film retarded electrochemical reactions. Micrographs of the quenched samples showed sigma and chromium carbide phases which prove the corrosion resistance of steel alloy.
Abstract: The nanofiber sheet of Multiwall Cabon Nanotube
(MWCNTs)/Polyacylonitile (PAN) composites was fabricated from
electrospun nanofiber. Firstly the surface of MWCNTs was
chemically modified, comparing two different techniques consisting
of admicellar polymerization and functionalization to improve the
dispersion and prevent the aggregation in the PAN matrix. The
modified MWCNTs were characterized by the dispersion in
dimethylformamide (DMF) solvent, Laser particle size, and FTRaman.
Lastly, DSC, SEM and mechanical properties of the
nanofiber sheet were examined. The results show that the mechanical
properties of the nanofiber sheet prepared from admicellar
polymerization-modified MWCNTs were higher than those of the
others.
Abstract: Effective cooling of electronic equipment has emerged
as a challenging and constraining problem of the new century. In the
present work the feasibility and effectiveness of jet impingement
cooling on electronics were investigated numerically and
experimentally. Studies have been conducted to see the effect of the
geometrical parameters such as jet diameter (D), jet to target
spacing (Z) and ratio of jet spacing to jet diameter (Z/D) on the heat
transfer characteristics. The values of Reynolds numbers considered
are in the range 7000 to 42000. The results obtained from the
numerical studies are validated by conducting experiments. From the
studies it is found that the optimum value of Z/D ratio is 5. For a
given Reynolds number, the Nusselt number increases by about 28%
if the diameter of the nozzle is increased from 1mm to 2mm.
Correlations are proposed for Nusselt number in terms of Reynolds
number and these are valid for air as the cooling medium.
Abstract: We estimate snow velocity and snow drift density on hilly terrain under the assumption that the drifting snow mass can be represented using a micro-continuum approach (i.e. using a nonclassical mechanics approach assuming a class of fluids for which basic equations of mass, momentum and energy have been derived). In our model, the theory of coupled stress fluids proposed by Stokes [1] has been employed for the computation of flow parameters. Analyses of bulk drift velocity, drift density, drift transport and mass transport of snow particles have been carried out and computations made, considering various parametric effects. Results are compared with those of classical mechanics (logarithmic wind profile). The results indicate that particle size affects the flow characteristics significantly.
Abstract: This research aims at modeling and simulating the effects of nanofluids on cylindrical heat pipes thermal performance using the ANSYS-FLUENT CFD commercial software. The heat pipe outer wall temperature distribution, thermal resistance, liquid pressure and axial velocity in presence of suspended nano-scaled solid particle (i.e. Cu, Al2O3 and TiO2) within the fluid (water) were investigated. The effect of particle concentration and size were explored and it is concluded that the thermal performance of the heat pipe is improved when using nanofluid as the system working fluid. Additionally, it was observed that the thermal resistance of the heat pipe drops as the particle concentration level increases and particle radius decreases.
Abstract: In distributed resource allocation a set of agents must assign their resources to a set of tasks. This problem arises in many real-world domains such as distributed sensor networks, disaster rescue, hospital scheduling and others. Despite the variety of approaches proposed for distributed resource allocation, a systematic formalization of the problem, explaining the different sources of difficulties, and a formal explanation of the strengths and limitations of key approaches is missing. We take a step towards this goal by using a formalization of distributed resource allocation that represents both dynamic and distributed aspects of the problem. In this paper we present a new idea for target tracking in sensor networks and compare it with previous approaches. The central contribution of the paper is a generalized mapping from distributed resource allocation to DDCSP. This mapping is proven to correctly perform resource allocation problems of specific difficulty. This theoretical result is verified in practice by a simulation on a realworld distributed sensor network.
Abstract: Phase locked loops (PLL) and delay locked loops (DLL) play an important role in establishing coherent references (phase of carrier and symbol timing) in digital communication systems. Fully digital receiver including digital carrier synchronizer and symbol timing synchronizer fulfils the conditions for universal multi-mode communication receiver with option of symbol rate setting over several digit places and long-term stability of requirement parameters. Afterwards it is necessary to realize PLL and DLL in synchronizer in digital form and to approach to these subsystems as a discrete representation of analog template. Analysis of discrete phase locked loop (DPLL) or discrete delay locked loop (DDLL) and technique to determine their characteristics based on analog (continuous-time) template is performed in this posed paper. There are derived transmission response and error function for 1st order discrete locked loop and resulting equations and graphical representations for 2nd order one. It is shown that the spectrum translation due to sampling takes effect at frequency characteristics computing for specific values of loop parameters.
Abstract: In this study a two dimensional axisymmetric, steady state and incompressible laminar flow in a rotating single disk is numerically investigated. The finite volume method is used for solving the momentum equations. The numerical model and results
are validated by comparing it to previously reported experimental data for velocities, angles and moment coefficients. It is
demonstrated that increasing the axial distance increases the value of axial velocity and vice versa for tangential and total velocities. However, the maximum value of nondimensional radial velocity
occurs near the disk wall. It is also found that with increase rotational Reynolds number, moment coefficient decreases.
Abstract: The Random Coefficient Dynamic Regression (RCDR)
model is to developed from Random Coefficient Autoregressive
(RCA) model and Autoregressive (AR) model. The RCDR model
is considered by adding exogenous variables to RCA model. In this
paper, the concept of the Maximum Likelihood (ML) method is used
to estimate the parameter of RCDR(1,1) model. Simulation results
have shown the AIC and BIC criterion to compare the performance of
the the RCDR(1,1) model. The variables as the stationary and weakly
stationary data are good estimates where the exogenous variables
are weakly stationary. However, the model selection indicated that
variables are nonstationarity data based on the stationary data of the
exogenous variables.