A study on the effect of building on the HF direction finding
The effect of new building on the high-frequency (HF) direction finding (DF) is analyzed. Commercially available software is used to get array manifold of the HF DF system taking the effect of the new building into account. The terrain, building and the array antenna system are modeled. The new building near the antenna system is also modeled to see whether it actually has an effect on the performance of the DF system. Interferometer DF algorithms has been employed.
Loop-dipole antenna modeling using the FEKO code
A study was done to optimize the design of a loop dipole antenna over a broad frequency range (0.5 - 2 GHz) using the FEKO method of moments code. Variations to the design were modeled as well as the performance of the antenna in an array. The modeling was compared to anechoic chamber data. The fields generated by the FEKO code were also input to a GTD (geometric theory of diffraction) code as an antenna pattern to model the multipath effects caused by mounting the antenna onto an aircraft.
Brushite-collagen composites for bone regeneration.
Brushite-based biomaterials are of special interest in bone regeneration due to their biocompatibility and biodegradability; on the other hand, collagen is a well-known osteoconductive biomaterial. In the present study a new brushite-collagen composite biomaterial is reported. This new biomaterial was prepared by combining citric acid/collagen type I solutions with a brushite cement powder. The obtained biomaterial was a cement paste, with improved handling properties. The effect of collagen on the setting reaction of brushite cement was studied, and was found to speed up the cement setting reaction. The cement paste set into a hard ceramic material within 18.5+/-2.1min and had compressive strength similar to that of spongeous bone (48.9+/-5.9MPa in dry conditions and 12.7+/-1.5MPa in humid conditions). The combination of collagen with citric acid revealed an interesting synergistic effect on the compressive strength of the composite material. Moreover, this new biomaterial had excellent cohesion properties (ninefold better than brushite cement), and high cellular adhesion capacity (threefold higher than brushite cement). The composite biomaterial described in this study combines good handling properties, compressive strength, cohesion and cell adhesion capacity, along with the osteoconductive and biodegradable properties inherent in brushite and in collagen-based biomaterials.