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  • Author: M. K. Ammar x
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S. M. El-Shaboury, M.K. Ammar and W.M. Yousef

Abstract

This paper introduces a different approach to obtain the exact solution of the relative equations of motion of a deputy (follower) satellite with respect to a chief (leader) satellite that both rotate about central body (Earth) in elliptic orbits by using Laplace transformation. Moreover, the paper will take the perturbation due to the oblateness of the Earth into consideration and simulate this problem with numerical example showing the effect of the perturbation on the Keplerian motion. The solution of such equations in this work is represented in terms of the eccentricity of the chief orbit and its true anomaly as the independent variable.

Open access

M. K. Ammar and D. A. Oda

Abstract

The goal of this paper is to find a combination of conical trajectories, using gravitational assisted maneuvers (swing-by), which perform the transfer from a nearby of the departure planet (Earth) to the vicinity of the arrival planet (Jupiter), making a closest approaches with Mars (flyby) to reduce the fuel consumption for the journey. A detailed description of the mission from Earth— Mars—Jupiter, that used this technique is presented. The table of flyby dates, altitudes of closest approaches is also included. A methodology known as the Patched Conics was used, where the trajectory is divided into three parts:

  1. Departure phase, inside of the sphere of influence of the departure planet,

  2. Heliocentric phase, during the journey between the planets,

  3. Arrival phase, inside the sphere of influence of the arrival planet.

Open access

Sarhan Y. Atwa, M. K. Ammar and Eman Ibrahim

Abstract

This paper is concerned on the distribution of a homogeneous isotropic elastic medium with diffusion under the effect of Three-phase-lag model. Normal mode analysis is used to express the exact expressions for temperature, displacements and stresses functions. Comparisons are made in the absence and presence of diffusion with some theories like Three-phase-lag and GNIII.

Open access

M. Almeselmani, A. Al-Rzak Saud, K. Al-Zubi, S. Al-Ghazali, F. Hareri, M. Al-Nassan, M.A. Ammar, O.Z. Kanbar, H. Al-Naseef, A. Al-Nator, A. Al-Gazawy and J.A. Teixeira Da Silva

Abstract

Water stress, which limits the distribution and productivity of durum wheat (Triticum durum Desf.) in the Mediterranean region, is also considered to be a major factor reducing yield in semiarid regions. Improving drought resistance is thus an important objective in plant breeding programs for rainfed agriculture. The current study was carried out to identify drought-tolerant durum wheat lines among 10 lines and one variety (Douma1, the control) in the first and second settlement zones in the Southern part of Syria and to recognize the most important physiological parameters associated with drought tolerance. Membrane stability index, chlorophyll (chl) content, relative water content and chl fluorescence were recorded at the vegetative and anthesis stages, as were yield and yield components. Data recorded at vegetative and anthesis stages in both zones showed that there were significant differences between all lines growing in the first and second settlement zones and that all characters in the second zone were significantly lower than those in the first zone. Line 1 was superior to Douma1 in terms of membrane stability index, relative water content, chl content and chl florescence, also showing better yield and higher total plant biomass, tiller number/m2, 1000 grain weight and grain number/ear than the control. The ability of wheat cultivars to perform reasonably well in variable rainfall and water-stressed environments is an important trait since it allows for stable production under drought stress. Moreover, prior to genetic manipulation, it is important to characterize the physiological parameters of known drought-tolerant or drought-sensitive wheat cultivars with the objective of better understanding their physiological responses under drought