The relations between Japan and the United States in space form a microcosm of the complex, multidimensional interactions between these two powerful societies. Cooperation and competition exist side by side, and the future balance between them is uncertain. The United States needs to develop a strategy with respect to future U.S.-Japanese space relations that balances national security, political, scientific, and economic interests. Crafting such a strategy is particularly difficult while both the United States and Japan debate the goals and content of their future space programs and while the two nations try to assess their broader interests and roles in the rapidly changing geopolitical environment. Essential to a productive approach to U.S.-Japanese space relations is an accurate understanding of the character and content of the Japanese space effort. 相似文献
The utility, vehicle required, the time needed for assembly and relocation and the costs associated with six different rainfall simulators were studied. The results can be summarized as follows:
1 The simulator designed by Kainz & Eicher (1990) is the least expensive to operate. This simulator also has excellent experimental versatility. Its only restriction is a short slope length.
2 The rainfall simulator of Karl & Toldrian (1973) is also inexpensive to operate, but because of disadvantages such as low falling height, wind susceptibility, and the need for more workers than other simulators, it should be used mainly where other simulators are not practical (forests, steep slopes, or long slopes).
3 The rainfall simulator of Richter et al. (1988) has limited mobility in the field and is highly susceptible to wind drift. Moreover, its narrow plots do not cover a representative unit of a cultivated field.
4 The modified Swanson-type simulator (Auerswald, (1986) is suitable for large plots if a sufficient water supply is available.
5 The simulator of Kromer & Vöhringer (1988) has the highest fixed costs, but labour is used efficiently.
6 The simulator of Schmidt (1983) can only be considered for stationary use because of its long assembly time. Other disadvantages are narrow plot size and high wind susceptibility.
Depending on the selection of the simulator, total costs of between 400 DM and 2000 DM per plot should be expected even with high use rates. 相似文献
The dominant large-scale pattern in the clouds of Venus has been described as a "gamma" or "Psi" and tentatively identified by earlier workers as a Kelvin wave. A detailed calculation of linear wave modes in the Venus atmosphere verifies this identification. Cloud feedback by infrared heating fluctuations is a plausible excitation mechanism. Modulation of the large-scale pattern by the wave is a possible explanation for the Y. Momentum transfer by the wave could contribute to sustaining the general circulation. 相似文献
Bacillus thuringiensis (B.t.) delta-endotoxins provide an alternative to chemical insecticides for controlling many species of pest insects. Recent biotechnological developments offer the promise of even greater use of B.t. toxins in genetically transformed pest-resistant crops. However, the discovery that insects can adapt to these toxins raises concerns about the long-term usefulness of B.t. toxins. Several methods for managing the development of resistance to B.t. toxins have been suggested, but none of these approaches offer clear advantages in all situations. 相似文献
In this two year study we investigated the effect that the level of concentrate in feedlot diet had on the occurrence of health problems in bull calves belonging to two multibreed groups.
In each of the two years, the 168 day feedlot period was divided into two equal periods of 77 days with an intervening 14 day adjustment period. During the first period, the animals in half of the pens within each breed-group received a high concentrate (85% grain) diet (H) while the rest of the pens received a diet (L) of hay ad libitum and half as much concentrate as the bulls on high concentrate. The L diet contained an average of 48% grain. In the second period, diets of bulls in half of the pens within each breed-group were switched from L to H and vice versa. During the feedlot period, the incidence of sickness among bulls was recorded. Disease incidence was higher in the second year compared to the first. In the second year, 49 out of 56 (87.5%) calves on the high concentrate diet required treatment for respiratory infections compared to only four (7.14%) in bulls on the low concentrate diet. The results suggest that a high concentrate diet for animals in feedlots may be more stressful to calves coming directly to the feedlot following weaning compared to a low concentrate diet, thereby acting as an additional predisposing factor to respiratory infections.