Abstract: This paper presents a vocoder to obtain high quality synthetic speech at 600 bps. To reduce the bit rate, the algorithm is based on a sinusoidally excited linear prediction model which extracts few coding parameters, and three consecutive frames are grouped into a superframe and jointly vector quantization is used to obtain high coding efficiency. The inter-frame redundancy is exploited with distinct quantization schemes for different unvoiced/voiced frame combinations in the superframe. Experimental results show that the quality of the proposed coder is better than that of 2.4kbps LPC10e and achieves approximately the same as that of 2.4kbps MELP and with high robustness.
Abstract: In this paper flow around two cam shaped cylinders had been studied numerically. The equivalent diameter of cylinders is 27.6 mm. The space between center to center of two cam shaped cylinders is define as longitudinal pitch ratio and it varies in range of
2 varies in range of 50
Abstract: With constraints on data availability and for study of power system stability it is adequate to model the synchronous generator with field circuit and one equivalent damper on q-axis known as the model 1.1. This paper presents a systematic procedure for modelling and simulation of a single-machine infinite-bus power system installed with a thyristor controlled series compensator (TCSC) where the synchronous generator is represented by model 1.1, so that impact of TCSC on power system stability can be more reasonably evaluated. The model of the example power system is developed using MATLAB/SIMULINK which can be can be used for teaching the power system stability phenomena, and also for research works especially to develop generator controllers using advanced technologies. Further, the parameters of the TCSC controller are optimized using genetic algorithm. The non-linear simulation results are presented to validate the effectiveness of the proposed approach.
Abstract: The objective of this paper is to present a research
study of the convectors that are used for heating or cooling of the
living room or industrial halls. The key points are experimental
measurement and comprehensive numerical simulation of the flow
coming throughout the part of the convector such as heat exchanger,
input from the fan etc.. From the obtained results, the components of
the convector are optimized in sense to increase thermal power
efficiency due to improvement of heat convection or reduction of air
drag friction. Both optimized aspects are leading to the more
effective service conditions and to energy saving. The significant part
of the convector research is a design of the unique measurement
laboratory and adopting measure techniques. The new laboratory
provides possibility to measure thermal power efficiency and other
relevant parameters under specific service conditions of the
convectors.
Abstract: Semiconductor detector arrays are widely used in
high-temperature plasma diagnostics. They have a fast response,
which allows observation of many processes and instabilities in
tokamaks. In this paper, there are reviewed several diagnostics based
on semiconductor arrays as cameras, AXUV photodiodes (referred
often as fast “bolometers") and detectors of both soft X-rays and
visible light installed on the COMPASS tokamak recently. Fresh
results from both spring and summer campaigns in 2012 are
introduced. Examples of the utilization of the detectors are shown on
the plasma shape determination, fast calculation of the radiation
center, two-dimensional plasma radiation tomography in different
spectral ranges, observation of impurity inflow, and also on
investigation of MHD activity in the COMPASS tokamak discharges.
Abstract: CDMA cellular networks support soft handover,
which guarantees the continuity of wireless services and enhanced
communication quality. Cellular networks support multimedia
services under varied propagation environmental conditions. In this
paper, we have shown the effect of characteristic parameters of the
cellular environments on the soft handover performance. We
consider path loss exponent, standard deviation of shadow fading and
correlation coefficient of shadow fading as the characteristic
parameters of the radio propagation environment. A very useful
statistical measure for characterizing the performance of mobile radio
system is the probability of outage. It is shown through numerical
results that above parameters have decisive effect on the probability
of outage and hence the overall performance of the soft handover
algorithm.
Abstract: The V-notches are most possible case for initiation of cracks in parts. The specifications of cracks on the tip of the notch will be influenced via opening angle, tip radius and depth of V-notch. In this study, the effects of V-notch-s opening angle on stress intensity factor and T-stress of crack on the notch has been investigated. The experiment has been done in different opening angles and various crack length in mode (I) loading using Photoelasticity method. The results illustrate that while angle increases in constant crack-s length, SIF and T-stress will decrease. Beside, the effect of V-notch angle in short crack is more than long crack. These V-notch affects are negligible by increasing the length of crack, and the crack-s behavior can be considered as a single-edge crack specimen. Finally, the results have been evaluated with numerical finite element analysis and good agreement was obvious.
Abstract: In the competitive environment of aircraft industries it becomes absolutely necessary to improve the efficiency, performance of the aircrafts to reduce the development and operating costs considerably, in order to capitalize the market. An important contribution to improve the efficiency and performance can be
achieved by decreasing the aircraft weight through considerable
usage of composite materials in primary aircraft structures. In this study, a type of composite material called Carbon Fiber Reinforced
Plastic (CFRP) is explored for the usage is aircraft skin panels. Even
though there were plenty of studies and research has been already
carried out, here a practical example of an aircraft skin panel is taken
and substantiated the benefits of composites material usage over the
metallic skin panel. A crown skin panel of a commercial aircraft is
designed using both metal and composite materials. Stress analysis
has been carried out for both and margin of safety is estimated for the
critical load cases. The skin panels are compared for manufacturing,
tooling, assembly and cost parameters. Detail step by step comparison between metal and composite constructions are studied
and results are tabulated for better understanding.
Abstract: Cyclic delay diversity (CDD) is a simple technique to
intentionally increase frequency selectivity of channels for orthogonal
frequency division multiplexing (OFDM).This paper proposes a residual
carrier frequency offset (RFO) estimation scheme for OFDMbased
broadcasting system using CDD. In order to improve the RFO
estimation, this paper addresses a decision scheme of the amount of
cyclic delay and pilot pattern used to estimate the RFO. By computer
simulation, the proposed estimator is shown to benefit form propoerly
chosen delay parameter and perform robustly.
Abstract: Since MEMS gyro sensors measure not angle of rotation but angular rate, an estimator is designed to estimate the angles in many applications. Gyro and accelerometer are used to improve estimating accuracy of the angle. This paper presents a method of finding filter coefficients of the well-known estimator which is to get rotation angles from gyro and accelerometer data. In order to verify the performance of our method, the estimated angle is compared with the encoder output in a rotary pendulum system.
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 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: 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: 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: 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: 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.
Abstract: In this paper, the noise maps for the area encircled by
the Second Ring Road in Riyadh city are developed based on real
measured data. Sound level meters, GPS receivers to determine
measurement position, a database program to manage the measured
data, and a program to develop the maps are used. A baseline noise
level has been established at each short-term site so subsequent
monitoring may be conducted to describe changes in Riyadh-s noise
environment. Short-term sites are used to show typical daytime and
nighttime noise levels at specific locations by short duration grab
sampling.