The construction of a fifth-order Jupiter-Saturn motion: Analytical theory

We construct a fifth-order with respect to masses Jupiter-Saturn secular theory by Hori-Lie canonical technique. The J-S Hamiltonian includes both parts of the perturbing function. The influence of the 2:5 critical terms is taken into consideration. The Jacobi-Radau system of origins is adopted and the theory is expressed in terms of the Poincaré canonical variables.     

Perturbation method in the theory of nonlinear oscillations

Asymptotic recurrence formulas for treating nonlinear oscillation problems are presented. These formulas are based on a Lie transform similar to that described by Deprit for Hamiltonian systems. It is shown that the basic formulas have essentially the same forms as those obtained by Deprit and by the present author in the Hamiltonian case.     

Recharge mode and mineralization of groundwater in a semi-arid region: Sidi Bouzid plain (central Tunisia)

Groundwater is the most important source of water supply in Sidi Bouzid plain located in central Tunisia. Proper understanding of the geochemical evolution of groundwater is important for sustainable development of water resources in this region. A hydrogeochemical survey was conducted on the Mio–Plio–Quaternary aquifer system using stable isotopes, radiocarbon, tritium and major elements, in order to evaluate the groundwater chemistry patterns and the main mineralization processes occurring in this system. The chemical data indicate that dissolution of evaporate minerals and evaporation are the main processes controlling groundwater mineralization. The isotopic data show that groundwater in the study area is a mixture of recent shallow waters located upstream and along Wadi Al Fakka bed and paleowaters located towards plain limits and discharge areas. Low ³H and ¹⁴C contents are observed in major part of the plain indicating that recharge of the aquifer occurs mainly through direct infiltration at Wadi Al Fakka while there is no evidence of significant recharge in major part of the plain and mountains piedmonts.     

Geologic hazards assessment of Cairo and vicinity

The greater area from Cairo to west of Suez and a smaller area directly around Cairo are subjected to general and detailed analysis of hazard due to geological fractures. Fracture density contour maps and rose diagrams of the fracture trends are provided. Possible natural geologic hazards which might affect the area are discussed. These include landslides, block failure, earthquakes, maars, fumarolic activity, hot springs, caves and possible rejuvenation of old fault systems.     

Geochemical study of groundwater mineralization in the Grombalia shallow aquifer,north-eastern Tunisia: implication of irrigation and industrial waste water accounting

Hydrochemistry of groundwater is largely determined by both natural processes, such as dissolution, cation exchange, mixing, evaporation; and anthropogenic activities, which can affect the aquifer systems by contaminating them or by modifying their hydrological cycle. Both natural and anthropogenic processes vary in time and space; which is reflected in groundwater hydrochemistry variation. The objective of this study is the determination of the main hydrogeochemical processes that affect the quality of shallow groundwaters in the Grombalia basin, located in the Cap Bon Peninsula, north-eastern Tunisia. In this area, the chemical composition of groundwater is mostly characterized by Na–Cl–NO₃–Ca water type which reveals the implication of natural and anthropogenic major factors. Natural factors are dissolution of evaporatic minerals, i.e. halite and gypsum and cation exchange with clays, while anthropogenic factors are pollution with industrial Sr-rich waste water and return flow of irrigation water, highly contaminated by MgSO₄ and methyl-bromide fertilizers.     

East-west stationkeeping requirements of 24-h satellites due to Earth's triaxiality and luni-solar effects

Ignoring luni-solar perturbations, analytical solution for longitude deviation of the ‘stroboscopic’ mean center of 24-h satellites ground trace in the neighborhood of a prespecified station is obtained. The initial semimajor axis for two-maneuver east-west stationkeeping is then deduced. Finally, the luni-solar long and short period effects on this initial semimajor axis are discussed.     

First-order secular planetary theory up to fourth power in eccentricities and inclinations

We construct a first-order secular general planetary theory, using the Jacobi-Radau set of origins, referring to common fixed plane and in terms of Poincaré canonical variables. We neglect powers higher than the fourth with respect to the eccentricities and sines of inclinations.     

Determination of secular terms in general planetary theory

A method to calculate secular terms of the two parts of the planetary disturbing function— when it is expressed in terms of the true anomalies or the eccentric anomalies instead of the mean anomalies - is described. Also an alternative method is outlined.     

Collision induced rotational excitation of AlF (X 1Σ+) by para-H2 (j=0)

Rotational excitation cross sections and rate coefficients of AlF collisions with para-H₂ are computed at low temperature, i.e., for T≤70 K. Prior to collisional calculations, a four-dimensional (4D) potential energy surface (PES) for the AlF-H₂ system is calculated at the ab initio Coupled-Cluster level of the theory with an aug-cc-pVQZ Gaussian basis set. This 4D-PES is further reduced to a two-dimensional (2D) PES based on the considerations related to collisional studies with para-H₂. The [Al-F] and [H-H] bond lengths are frozen at their experimental equilibrium value r _e =1.654369 bohr and r _e =1.4011 bohr respectively. The interaction energy presents a global minimum located ∼63 cm⁻¹ below the AlF-H₂ dissociation limit. With this PES, cross sections are determined in the Close-Coupling (CC) approach and rate coefficients are inferred by averaging the cross sections over a Maxwell-Boltzman distribution of kinetic energies. These quantities are significantly magnified in comparison with their AlF-He counterparts. The already observed propensity towards ΔJ=1 transitions for AlF-He remains.