Journal of Engineering and Sustainable Development (JEASD)

A theoretical analysis of the coupled-cavity semiconductor laser requires simultaneous consideration of the gain and loss in the two cavities after taking into account their mutual optical feedback. Is wavelength-independent (and hence the same for all Fapry-perot (FP), in a coupled-cavity laser the effective facet loss becomes different.

The turbulent buoyancy induced flow and heat transfer characteristics inside U-shaped enclosure has been numerically documented. Fully elliptic Navier-Stockes and energy equations are solved using control volume based finite volume method with a staggered grid arrangements. A computer program using SIMPLEC algorithm is developed to handle the problem of interest. The effect of Rayleigh number and aspect ratio on the studied parameters are examined. The problem is simulated for Ra up to 1016 and aspect ratio of (0.25, 0.35 and 0.5). The k-є model is engaged with the flow equations to model the turbulence while the wall function method is used to model the regions near the walls. The present results show that the aspect ratio and Ra have a significant effect on the flow and thermal characteristics. The rate of heat transfer is increased with the decrease of aspect ratio and increase with Ra. A multi cellular flow has been obtained at decreasing the aspect ratio for Ra up to 1012.

The purpose of this paper is to solve the nonlinear rate equations of directly modulated semiconductor laser by direct simulation (numerical solution) where the rate equations are described the dynamic behavior of semiconductor laser because of optical field is depended on the time. The other side, the rate equations are described the interactions among photon density ,carrier density ,and the phase of photon .However ,these equations are used to predict the nonlinear distortions which it is appeared in the performance of directly modulated semiconductor laser.

This investigation deals with the performance prediction of cross-flow air-cooled heat exchangers. Experimental work was carried out on a finned tube air-cooled heat exchanger. A water supplying system rig was built for this object which provides water at a temperature range of (10 to 50)°C with a water circulating rate up to (2000) l/hr. Air volumetric flow rates of (500,1000 and 2000) cfm at a temperature of (32)ºC were used during the experiments. A two-dimensional model was suggested to perform the core dimensions prediction of the air-cooled heat exchanger. This model was based on the step-by-step technique which is suggested to divide the height and depth dimensions of the heat exchanger into slices and rows respectively. The thermal performance represented by heat load, heat transfer coefficient (airside), overall heat transfer coefficient, and air exit temperature from the heat exchanger were predicted by the present model. The suggested simulation model showed that the maximum discrepancy between the predicted and experimental values of the heat exchanger performance was about (3%).

Fluid coupling is regarded as an essential mechanism in semi-automatic transmission systems which are used in most new and advanced heavy vehicles . It has already replaced the ordinary mechanical coupling and clutch units . It has a great advantage of reducing torsional and transverse vibrations. In addition , changing gear ratios can be accomplished easily without difficulty . Curve fitting technique with the aid of computer has emerged as a compelling animation technique . Yet current approaches to fluid coupling simulation are inefficient or can\'t handle some relevant scenarios robustly . A practical results of a certain fluid coupling has been chosen which were used in \" Reem \" buses and were utilized by the State Company for Automotive Industries at Iskanderia in Iraq . However , and when modeling the complete engine transmission system , these practical results were not easy to follow and apply . The aim of this work is to develop a simple and flexible model for a fluid coupling . The object is to obtain a simple relation among fluid coupling main controllable variables , so that is can be utilized easily in a future comprehensive model of engine-transmission system used for dynamic analysis.

The quality of groundwater in Zhengzhou area is important as many individuals depend on groundwater for drinking. A study on shallow groundwater quality assessment in Zhengzhou area, China has been done using Remote Sensing and Geographic Information System (GIS) techniques. The land use/cover classification system and remote image interpretation of characteristics were established in this process. Land types were divided into six categories: water resources, forest land, grass land, barren land, Residential areas, and crop land. Water Quality Index was also calculated for sixty three well samples in the study area to evaluate the suitability of water for human consumption. The results show that the grass land is the greatest proportion of land use/cover in the study area (37.59%), the residential area comprises 13.52%, the area of crop land occupies 22.54%, and the barren land occupies 21.81%. Water Quality Index (WQI) values revealed that the groundwater at twelve locations of the study area are Excellent quality. Twenty wells are V. good quality, and fourteen wells are Good quality, therefore can be exploited safely for human consumption. Six well samples are Fair quality, nine samples are Marginal quality, and two samples are Poor (unfit).

Reinforced earth has been applied for different types of load supporting and retaining structures in more confidence throughout the world. In this study, the finite element method is implemented and used to analyze reinforced earth walls. The computer program SIGMA/W is used in the analysis of plane strain problems. Eight node isoparametric elements are used to model the soil while structural elements having nodes that match with the surrounding elements, are used to model the reinforcement material. A parametric study is carried out to investigatethe effect of different parameters on the general behaviour of reinforced earth walls. These parameters include: the height of the wall (H), length of reinforcement (L) and external loads (static and cyclic). Three different heights were tried (3, 5, 7) m and three value of load (q) were used (5, 20, 50) kN/m². It was found that the wall with a small height (3 m) tends to translate and overturn about its foundation to the out, while the walls with greater heights (5m), translate to the out, and the horizontal displacement increases with depth.

The present investigation is concerned with the alternatives used for the cooling load reduction of a space in Baghdad. A numerical and experimental study has been accomplished in Baghdad during July and August of 2008 with the application of a new technique by a suitable alternative for minimizing the cooling load. In the experimental side of this work, a vertical aluminum flat plate is situated on the eastern and southern walls. This sheet is extended into the under ground to a depth of (1) m of a cube test room having (1) m3 size. The experimental data showed that the indoor temperature reduced from (34.5) °C to (31.7) °C and (29.9) °C when using aluminum plate with air gap and glass wool insulation respectively. The heat flux on the southern wall reduced by (23.5%) and (33.7%) for air gap and glass wool respectively. The corresponding reductions on the eastern wall were (20%) and (29.8%) for air gap and glass wool respectively. A numerical simulation two-dimensional model was performed applying a finite difference technique implemented in a sophisticated MATLAB program.

This paper presents a theoretical approach for estimating the draught force in front of a bulldozer blade. Forces required to produce any kind of soil failure can be described by an additive equation. Advantage was taken by Reece’s family of curves from which will be possible to obtain a ready solution to most two – dimensional passive pressure problems. An equation has been simplified making certain assumptions. Then an example for application was solved obtaining the required power for bulldozer to do a certain job. It is hopped that this paper will be useful, especially when choosing the right design of a bulldozer blade for a required purpose

The Field Programmable Gate Array (FPGA) approach is the most recent category, which takes the place in the implementation of most of the Digital Signal Processing (DSP) applications. It had proved the capability to handle such problems and supports all the necessary needs like scalability, speed, size, cost, and efficiency. In this paper a new proposed circuit design is implemented for text coding with an implemented example using FPGA is provided. In this implementation, the evaluations of the text coefficients are evaluated on the Scrambling – Coding, and the De-Scrambling - De-Coding sides. This implementation was achieved using an FPGA Kit after building the logical circuits on the specified kit that uses the Spartan-XL electronic library type implemented using the ISE-4.1 software which is one of the latest versions of the Xilinx Foundation Series 2.1I software.

Image encryption is one of the most important applications in transferring images through the internet. In most of the natural images the values of the neighboring pixels are strongly correlated. This means that the value of any given pixel can be reasonably predicted from the values of its neighbors. This paper presents an approach for image encryption based on combination of image scrambling and well known encryption and decryption algorithms such as RC4 and AES. The original image can be viewed as an arrangement of pixels, which were rearranged into a scrambled image using pseudo random index generator, and then the generated image was encrypted using one of the encryption algorithm. The results showed that the correlation between image elements was significantly decreased by the proposed technique. Also, a number of performance measuring factors were considered to show the impact of the proposed technique.

A modulation of the device current leads to laser-power modulation and is useful for transmitting information as a sequence of optical pulses .However , modulation of the current also affects the optical frequency which emphasize that carriers influence the optical phase . The center frequency of the out put laser shifts by an amount during modulation . The phenomenon of the dynamic shift of the laser frequency is referred to as frequency chirping or wavelength chirping . The chirp is directly proportional to the line-width enhancement factor and has its origin in the carrier induced index change that accompanies any gain change in semiconductor laser . This chirp may be reduced by a suitable shaping of the injection current.

This research is a study of the solid wastes in Karbala city. This study includes the identification of solid waste characteristics (generation rates, physical components, moisture content, density). The examinations have been done on the waste for eight months with one examination in a month as a rate, for the period from December 2007. until July 2008. , to take into account the changes of the seasons. The results show that the rate of generation was 0.44 kg/ person/ day, the density of waste was 469 kg/m, and moisture content was 48%. A study of the principal components of the (leachate) which migrates from the solid waste at the dumping site was done, and samples were taken from the leachate at the dumping site for five-month from December 2007. until March 2008. Eight tests have been done (Biochemical oxygen demand, chemical oxygen demand, Alkalinity, calcium ions, Sodium ions, Total suspended solids, Total dissolved solids, and Iron ion. In addition to that , a management system has been achieved to manage the solid waste of the city in addition to the recommendations which guarantee to reduce the risks of this problem