Pitfall Trapping of Microtus townsendii
A field population of Microtus townsendii was trapped concurrently with live-traps and pitfall traps throughout the spring and summer of 1975. The population was at peak densities, with a maximum of 519 voles per acre. The number enumerated by pitfalls was up to two times larger than the number enumerated by live-traps. Capture of a large number of young in pitfalls indicated that mortality was higher among post-weanlings than among any other age group. Recruitment to live-traps was largely restricted to animals over 40 g, whereas in pitfalls animals were generally lighter. Over half of the 1,100 animals captured first by pitfalls were never caught by live-traps. Among those subsequently entering live-traps, many stayed away for 6 to 10 weeks, and some of the smaller ones stayed away even longer. Few animals dispersed to other nearby trapping grids. Pitfall trapping and live-trapping sample different subpopulations, young animals and transient adults being a large fraction of the individuals caught in pitfalls.
Small mammal fauna of two abandoned field habitats, and a spatio-temporal analysis of four rodent populations
: In the present study the authors investigate the small mammal fauna of two abandoned field habitats with different vegetation in the Dráva Lowlands, and the spatio-temporal changes of four rodent species found there, based on live-capture data from 1997-1998. The sampling areas are situated in the plain area of the rivulet Fekete-víz: one near the village Páprád, in a swampy area, which was not cultivated for four years, and the other near the village Nagycsány, in an area, which had been abandoned for one year. Based on their small mammal diversities, the two areas did not differ. Four species were captured in great numbers in both of the habitats: M. arvalis, A. agrárius, A. sylvaticus and A. flavicollis. For the characterisation of their dynamics, we applied minimum number alive (MNA) values, and for describing the spatial distribution of the individuals within the population, Lloyd's patchiness was used.
Turbine blade temperature calculation and life estimation - a sensitivity analysis
Abstract The overall operating cost of the modern gas turbines is greatly influenced by the durability of hot section components operating at high temperatures. In turbine operating conditions, some defects may occur which can decrease hot section life. In the present paper, methods used for calculating blade temperature and life are demonstrated and validated. Using these methods, a set of sensitivity analyses on the parameters affecting temperature and life of a high pressure, high temperature turbine first stage blade is carried out. Investigated uncertainties are: (1) blade coating thickness, (2) coolant inlet pressure and temperature (as a result of secondary air system), and (3) gas turbine load variation. Results show that increasing thermal barrier coating thickness by 3 times, leads to rise in the blade life by 9 times. In addition, considering inlet cooling temperature and pressure, deviation in temperature has greater effect on blade life. One of the interesting points that can be realized from the results is that 300 hours operation at 70% load can be equal to one hour operation at base load.