生物炭施用对夏填闲糯玉米磷素吸收及土壤磷素层间运移影响研究

华北设施农田磷淋失的问题严重,本文通过不同用量生物炭配合糯玉米,即CK (0%)、C1 (0%)、C2 (0.5%)、C3 (2%)、C4 (4%)、C5 (8%),研究在夏季如何阻控和缓解磷淋失以及减少磷累积的问题。结果表明,随着生物炭用量增加,填闲糯玉米生物量以及吸磷量均出现先增加后减小的特点,其中C2 (0.5%)处理最大,土壤全磷及水溶性磷均有减少,C2 (0.5%)为最优处理,其全磷降低了2.68%,水溶性磷0~30 cm表层下降了37.8%,90~120 cm土层下降幅度达到85.3%。因此,在本试验条件下得出0.5%~2%生物炭施用水平为最佳用量范围,即添加185~750 kg•hm−2最有利于阻控和缓解磷素的淋失问题。

Seismic Performance of Dry-Friction Devices in Shear-Frame Buildings

In recent years the application of friction-based passive energy dissipation devices have been proven very effective in reducing structural response to earthquake excitations and also implemented for a large number of buildings. Their design heavily relies on numerical simulations to model the influence of the energy dissipation devices. The modeling of friction forces must be accurate for realistic simulation of the influence of these devices. In state-of-the-practice, the hysteretic behavior of friction devices has been typically modeled with Coulomb friction having a constant coefficient of friction. However, the basic laws for typical sliding materials and experimental investigations show non-linear relationship between friction and sliding velocity, which includes stiction and Stribeck effect. The influence of stiction and Stribeck effect may be significant and can not be ignored in simulating the dynamic responses of structures with friction-based energy dissipation devices. In this paper the optimal performance of dry friction device in shear-frame buildings when subjected to earthquake ground motions has been investigated. The focus of this paper is on the optimal minimization of response of the shear-frame building. Since buildings with friction devices behave in a highly nonlinear manner, nonlinear response-history analysis considering comprehensive sliding friction models has been carried out. The performance has also been evaluated using the various response measures： the maximum absolute acceleration, the maximum base shear, and the maximum inter-story drift. Different performance indices have been used to quantify the influence of the device properties.