Radiation from an axial electric dipole with prolate spheroidal metamaterial cloak cover
Exact analytical expressions for the electromagnetic field due to a dipole source located inside and along the axis of symmetry of a prolate spheroid are provided.
Exact dipole radiation for an oblate spheroidal cavity filled with isorefractive material and aperture-coupled to a half space
An oblate semi-spheroidal cavity flush-mounted under a metal plane and coupled to the half-space above it via its circular interfocal aperture is considered. The cavity is filled with a material isorefractive to the medium that occupies the half-space above it. An exact solution is obtained for the radiation of an electric or magnetic dipole located on the symmetry axis of the structure, either outside or inside the cavity, and axially oriented. Numerical results are provided.
Improving water use in agriculture : experiences in the Middle East and North Africa
Emerging water shortages are of great concern in many countries of the region. As the agricultural sector is generally by far the most important water consumer and higher priority is given to meeting domestic and industrial water demands, it is to be expected that gradually less water will be available for agriculture. An overview is given of present system and on-farm water use efficiencies and the potential for water savings and yield increases through the use of improved distribution networks and more appropriate irrigation technologies for smallholders. The water conservation efforts of Israel, Cyprus and Jordan are examined in detail with respect to institutions, the irrigation infrastructure, water charges and demand management, operation and maintenance, irrigation scheduling and extension, technology development and transfer, the role of the private sector, quality control on irrigation equipment, land tenure and land consolidation, and water users associations. The World Bank's experience with lending for the irrigation sector in the region is also described. The elements that would need to be considered for inclusion in a national program for water conservation in the agricultural sector are identified.