海上大兆瓦风电锻造行星架调质裂纹失效分析

通过硬度测定、金相组织检验和化学成分分析等手段,对海上大兆瓦风电锻造行星架调质裂纹原因进行失效分析。结果表明:内孔碳元素含量超上差和铸造树枝晶偏析残留是海上大兆瓦风电锻造行星架调质后弧形裂纹的主要原因,淬火冷却因素是弧形裂纹的次要原因。通过对钢锭的选型及质量控制优化、反偏析加工技术以及调质工艺工装的研发,海上大兆瓦行星架调质裂纹问题得以消除,实现风电锻造行星架无裂纹质量特征。

基于EMD-Hilbert的行星齿轮箱在线故障诊断

针对风电机组行星齿轮箱传动过程中行星齿轮磨损对其他部件所造成的损伤,提出了一种基于经验模态分解(EMD)、Hilbert解调技术(HT)的风电机组行星齿轮箱齿轮磨损在线故障诊断方法。首先,以行星齿轮箱传动系统为研究对象进行信号采集并进行降噪预处理;然后,通过EMD对信号进行分解,根据时域信号指标参数计算分解后信号的IMF分量,重组、求取幅值谱;最后,利用Hilbert包络解调分析得到重组后的调制信号的包络解调谱,结合调制信号的包络解调谱频率以及行星齿轮箱各部件的故障特点实现故障诊断。实验结果表明,基于EMD-Hilbert的方法对风电机组行星齿轮箱传动系统在线故障诊断具有很好的判别效果。

华东喀斯特地貌发育过程与古地理背景

本文探讨古地理环境与喀斯特发育的关系。认为本区喀斯特地貌发育过程的特点是:从行星风型到季风型喀斯特,具有不同强度的多期性,造成南北方喀斯特形态归并与兼容,以及南北过渡性与区域分异。

今年的节气与天象

虎年“两头春”１９９８年和１９９９年的“立春”都是２月４日，农历戊寅年开始于１９９８年１月２８日（春节），结束于１９９９年２月１５日（除夕）。这样，虎年中就包含了两个“立春”，民间俗称为“一年两头春”。节气是根据太阳在黄道上的位置而确定，实际上是阳历...

Impacts of boundary layer parameterization schemes and air-sea coupling on WRF simulation of the East Asian summer monsoon

The planetary boundary layer （PBL） scheme in the regional climate model （RCM） has a significant impact on the interactions and exchanges of moisture, momentum, and energy between land, ocean, and atmosphere; however, its uncertainty will cause large systematic biases of RCM. Based on the four different PBL schemes （YSU, ACM2, Boulac, and MYJ） in Weather Research and Forecasting （WRF） model, the impacts of these schemes on the simulation of circulation and precipitation during the East Asian summer monsoon （EASM） are investigated. The simulated results of the two local turbulent kinetic energy （TKE） schemes, Boulac and MYJ, are more consistent with the observations than those in the two nonlocal closure schemes, YSU and ACM2. The former simulate more reasonable low-level southwesterly flow over East China and west pacific subtropical high （WPSH） than the latter. As to the modeling of summer monsoon precipitation, both the spatial distributions and temporal evolutions from Boulac and MTT are also better than those in YSU and ACM2 schemes. In addition, through the comparison between YSU and Boulac experiments, the differences from the results of EASM simulation are more obvious over the oceanic area. In the experiments with the nonlocal schemes YSU and ACM2, the boundary layer mixing processes are much stronger, which lead to produce more sea surface latent heat flux and enhanced convection, and finally induce the overestimated precipitation and corresponding deviation of monsoon circulation. With the further study, it is found that the absence of air-sea interaction in WRF may amplify the biases caused by PBL scheme over the ocean. Consequently, there is a reduced latent heat flux over the sea surface and even more reasonable EASM simulation, if an ocean model coupled into WRF.

Three-dimensional MHD simulation of the lunar wake

We study the interaction between the Moon and the solar wind through a three-dimensional MHD simulation.Three cases have been discussed in which the interplanetary magnetic field lies at 90,180,and 135 to the solar wind flow,respectively.A wake with low density and low pressure can always be formed behind the Moon.The plasma temperature and magnetic field are enhanced in the central wake,but the field strength is reduced in the surrounding region.A Mach cone is formed by rarefaction waves emanating from the limb.These rarefaction waves propagate via the fast magnetosonic mode with different velocities in different directions relative to the magnetic field.When the interplanetary magnetic field is not parallel to the solar wind flow,the wake shows some asymmetries,with an acceleration region turning up at the center.Finally,the results are compared with the observations by WIND spacecraft.Our calculations agree reasonably well with the observed values.