Articles in This Issue
Abstract
Serial Concatenation Convolutional Codes (SCCCs) encoder is built using a serial concatenation of two Recursive Systematic Convolutional (RSC) encoders, separated by an interleaver. These two RSC encoders depending on the trellis termination criteria are software implemented and the performance of each one of them is analyzed under different conditions and circumstances. The output data from the encoder are multiplied by an amplitude matrix (AM) at the transmitter side and the Inverse of Amplitude Matrix (IAM) at the receiver side. The reliability estimation, log-likelihood algebra, and soft channel outputs for Soft Output Viterbi Algorithm (SOVA) are examined. Then the modified Viterbi metric that incorporates a-priori information used for SOVA decoding is derived. A low memory implementation of the SOVA decoder is presented. The iterative SOVA for SCCCs is described with illustrative examples. The behavior of the SCCCs encoder-decoder scheme is tested under different circumstances with AM and without AM at the AWGN and Rayleigh fading channels with unlike frame sizes (FS) and constraint length (K). The results show that the performance of system with AM outperforms the other conventional system that worked without AM.
Abstract
In satellite communications with frequencies above 10GHz the major problems in radio-wave propagation is signal level attenuation caused by tropospheric scintillation, together with signal level attenuation by rain. There are several methods to measure the magnitude of scintillation. The equations of most of these methods do not include meteorological element. In meantime we can not measure the magnitude of scintillation with elevation angle 5¢ھ-10¢ھ. A prediction method is suggested to measure tropospheric scintillation on earth-space path. It would apply this method to standard atmosphere and we studied the effect of meteorological conditions, frequency, antenna diameter and elevation angle on the magnitude of scintillation.
Abstract
The Digital control systems for substations have been installed in different areas of Iraq in the recent years. Most of these techniques used a Supervisory Control And Data Acquisition (SCADA) with Remote Terminal Unit (RTU) for monitoring the metering devices for incoming and outgoing feeders, while the other system used a Programmable Logic Control (PLC) technique for controlling and monitoring the system inside substations by professional engineers. A practical monitoring system of SCADA with RTU has been introduced in this paper for Falluja substation. There are 3 devices of RTUs are used to collect data from ION 6200 devices installed inside incoming and outgoing panels for low Voltage (LV 380V), 33KV and 11KV, then the data from each RTU will be send to the SCADA (main Computer) via special router, the SCADA system used ION enterprise software supplied by AREVA company in addition to all panels which supplied by the same company. Many difficulties were appeared during the work, such as mistakes of IPs, setting parameters, selection of protocols, and matching of devices have solved until the normal work was obtained to the substation.
Abstract
This paper deals with the transient interlaminar thermal stress analysis of angle-ply SIC/LAS composite cantilever plate due to sudden change in the thermal boundary conditions .The transient interlaminar thermal stresses are computed by using the finite element method for different intervals of time. The effects of the fiber volume fraction, fiber orientation angle and stacking sequence are studied. The results are compared with previous studies with a good agreement
Abstract
In this paper, a proposed structure was suggested by replacing the blocks of the fast Haar Wavelet Transform (WT) with a two dimensional wavelet transform at the transmitter and the receiver sides in the Orthogonal Frequency Division Multiplexing (OFDM) model. This can be done by converting a 1-Dimensional vector into a 2-Dimensional matrix and process it by 2-Dimensional Wavelet Transform (2D-WT). The proposed method was applied on the OFDM in Additive White Gaussian Noise (AWGN) and flat fading channel. It was concluded that the proposed method gives much better Bit Error Rate (BER) performance than the conventional OFDM model based on WT. The simulation results showed that the proposd structure outperforms the other scheme in the carried tests at the AWGN and flat fading channels.
Abstract
Experiments were carried out on natural convection heat transfer from longitudinal trapezoidal fins array heat sink subjected to the influence of orientation. A trapezoidal fins heat sink with various orientations tested under a controlled environment. Test results indicate that the sideward horizontal fin orientation yield the lowest heat transfer coefficient. However the sideward vertical fin orientation gave the best performance on the natural cooling. From the experiments Nu is determined as a function of Ra at Pr=0.7 for each orientation with Ra ranging between (1400 and 3900).From the results; Heat transfer coefficient of the sideward vertical fins is higher by (12%) than the heat transfer coefficient of the upward while it is higher than the heat transfer coefficient of the downward by (26%) and by (120%) with the sideward horizontal fins. Orientation affected the temperature distribution along the fins, therefore the temperature along the sideward vertical fins have the best performance with uniform distribution, while in sideward and downward the temperature increased in the positions near the base plate surface because of the complication in moving the heated air.
Abstract
In the Present work, the application of the PLC in the production line was studies from the point view of industrial engineering and write program by ladder diagram (LAD) method. This study was done in ceramic factory of the state company of class and ceramic in Ramadi. It was exactly on the Kiln entrance of ceramic tiles, for reused PLC system where the tiles pieces inter the Kiln in compiled arranged rows in order to guarantees the heat distribution
Abstract
A Numerical study has been conducted to clarify the effect of the buoyancy forces on the thermal development through a horizontal annulus sector heated with constant surface temperature. The study includes the solution of governing equations for the flow and heat transfer of different sections along the channel. Theoretically these governing equations were reduced to four, which are continuity equation, radial and tangential momentum equations, axial momentum equation and vorticity equation in which the variables were the temperature, vorticity, stream function and axial velocity. These equations were reduced to dimensionless equations in which Rayleigh, Prandtl and Reynolds numbers were presented. They were numerically solved by using the marching process explicit finite difference method and Gauss elimination technique. Numerical results for annulus sector heated by constant surface temperature for different values of Rayleigh numbers and total sector angles and diameters ratio were obtained and represented by stream function contours and isotherms and circumferential distribution of local Nusselt number. Also the results include the values of friction factor and average Nusselt number for the pure forced convection. Comparisons are made between the computed results and the analytical or numerical results available in the literature, for all cases compared, satisfactory agreement is obtained. The results include a survey of annulus sector surface in many sites of channel flow, whereas it is apparent that the buoyancy force causes the secondary flow to behave non uniformly at the entrance and then the average heat transfer will increase with the increasing both of diameter ratio and total annulus sector angles. A correlation relationship is extracted to find an average change of Nusselt after the stability of the flow in the fully developed region for the studied ranges of annulus sector angles and diameters ratio.
Abstract
This research work includes study of sound insulation property of concrete samples with different densities. This study intended to present a proposed empirical formula to determine the sound insulation of concrete walls using the ultrasonic instrument. Experimental tests on concrete samples were made using the ultrasonic instrument, the sound insulation of concrete walls calculated according to a proposed empirical formula made in this work. This formula takes into consideration pulse velocity, wall width, and frequency .This formula is supported on a statistical criteria. The results are evaluated and compared with the values that computed using the most well-known formula, the comparison show compatibility of the results with tolerance of (3%).