Animal performance is affected by high air temperature and it is known that shade reduces the absorption of radiant temperature, and water for immersion facilitates heat loss. This study intends to find preferences of...Animal performance is affected by high air temperature and it is known that shade reduces the absorption of radiant temperature, and water for immersion facilitates heat loss. This study intends to find preferences of resources that contribute for the well-being of cattle and how they alterdaily behaviour. During summer, six Caracu and six Red Angus bulls were submitted to two different treatments： availability of artificial shade and water for immersion and availability of water for immersion. The categories observed were： positions （in the sun, under the shade, in the water）, posture （standing, lying down） and activities （grazing, ruminating leisure）. The behavioural patterns were recorded using the focal sampling method every 15 minutes （from 6：00 a.m. to 6：00 p.m.）. When shade and water for immersion coexists, cattle in this study prefer shade to avoid solar radiation. Both breeds had remained more time grazing, followed by ruminating in the Caracu breed, and by resting in the Red Angus breed. The Caracu breed had presented clear preference for the shade resource, but that fact was not always observed in the Red Angus breed. In hot climates, resources for defence against heat load, as shade and water for immersion improve the well-being of cattle.展开更多
Solar sail is used to achieve a geocentric sun-synchronous frozen orbit.This kind of orbit combines the characteristics of both sun-synchronous orbits and frozen orbits.Furthermore,the impossible orbits for a typical ...Solar sail is used to achieve a geocentric sun-synchronous frozen orbit.This kind of orbit combines the characteristics of both sun-synchronous orbits and frozen orbits.Furthermore,the impossible orbits for a typical spacecraft such as sun-synchronous orbits whose inclination is less than 90° are also possible for solar sail.To achieve a sun-synchronous frozen orbit,the characteristic acceleration of the sail is chosen properly.In addition,the attitude of the sail is adjusted to keep the sun-synchronous and frozen characteristics.The perturbations including atmosphere drag,third-body gravitational forces and shaded regions are discussed,where the atmosphere drag is cancelled by solar radiation pressure force,third-body gravitational forces have negligible effects on the orbit and the shaded region can be avoided by choosing the classical orbit elements of the sail.At last,a numerical example is employed to validate the sun-synchronous frozen characteristics of the sail.展开更多
文摘Animal performance is affected by high air temperature and it is known that shade reduces the absorption of radiant temperature, and water for immersion facilitates heat loss. This study intends to find preferences of resources that contribute for the well-being of cattle and how they alterdaily behaviour. During summer, six Caracu and six Red Angus bulls were submitted to two different treatments： availability of artificial shade and water for immersion and availability of water for immersion. The categories observed were： positions （in the sun, under the shade, in the water）, posture （standing, lying down） and activities （grazing, ruminating leisure）. The behavioural patterns were recorded using the focal sampling method every 15 minutes （from 6：00 a.m. to 6：00 p.m.）. When shade and water for immersion coexists, cattle in this study prefer shade to avoid solar radiation. Both breeds had remained more time grazing, followed by ruminating in the Caracu breed, and by resting in the Red Angus breed. The Caracu breed had presented clear preference for the shade resource, but that fact was not always observed in the Red Angus breed. In hot climates, resources for defence against heat load, as shade and water for immersion improve the well-being of cattle.
基金supported by the National Natural Science Foundation of China (Grants Nos.10902056 and 10832004)State Key Lab of Astronautical Dynamics of China (Grant No. 2011ADL-DW0201)
文摘Solar sail is used to achieve a geocentric sun-synchronous frozen orbit.This kind of orbit combines the characteristics of both sun-synchronous orbits and frozen orbits.Furthermore,the impossible orbits for a typical spacecraft such as sun-synchronous orbits whose inclination is less than 90° are also possible for solar sail.To achieve a sun-synchronous frozen orbit,the characteristic acceleration of the sail is chosen properly.In addition,the attitude of the sail is adjusted to keep the sun-synchronous and frozen characteristics.The perturbations including atmosphere drag,third-body gravitational forces and shaded regions are discussed,where the atmosphere drag is cancelled by solar radiation pressure force,third-body gravitational forces have negligible effects on the orbit and the shaded region can be avoided by choosing the classical orbit elements of the sail.At last,a numerical example is employed to validate the sun-synchronous frozen characteristics of the sail.
