三维裂纹整体参数化模化方法

发展一种独立于几何结构基于参数设计的三维平片裂纹扩展有限元模拟通用方法.该方法通过包含整个裂纹面的镶嵌裂纹模型,具有裂纹体自动形成,模拟裂纹多自由度扩展的能力.通过多个典型的工程裂纹扩展模拟算例,说明该方法的精度、效率与通用性.      

Fuzzy energy-based dual contours model for automated coronal hole detection in SDO/AIA solar disk images

The presence of coronal holes in solar disk plays an important role in influencing the space weather and generation of the solar wind. As such there lies a requirement in proper study and prediction of coronal holes occurs in the solar disk. This, in turn, arises the necessity of detection of coronal holes present in the solar disk. In this work, a Hough transformed inspired fuzzy-energy simulated dual contours-based segmentation technique has been proposed for the detection and extraction of holes in solar disk. In the proposed method Hough transform has been induced to initialize the contour for the contour-based method of segmentation. In the algorithm, two contours (active and static) have been initiated and made to evolve based on the energy function by incorporating the gray-scale intensity. Here in the work one contour is made to deform its shape while the other contour is kept static for the coronal holes detection purpose. The experiment has been carried out on few benchmark datasets and the corresponding outcomes have been compared with the results of other existing algorithms. The comparison results highlight the performance of the proposed technique in detection of coronal holes in solar disk.     

基于名义极限因子和降维方法的涡轮盘结构可靠性优化

结合名义极限因子方法完全实现了可靠性分析与优化过程的解耦,使可靠性分析成为进行优化之前的预分析过程,而在预分析中采用的基于降维的可靠性分析技术,在一阶可靠度方法(FORM)获得的计算结果的基础上进行适晕的数值计算就能够提高可靠性分析的结果.最后,以某涡轮盘结构优化为例对提出的方法可行性和效率进行了验证,结果表明:该方法...     

带盖板预旋系统的流动实验

通过低转速的模拟实验对涡轮盘腔的带盖板预旋系统的流动特性进行了研究。在不同的紊流参数（0.5〈λT〈0.96）和旋转比（1.03〈βp〈1.9）下测量了预旋腔和盖板腔内的压力与速度分布,得到了两个腔内的旋转比变化情况,并分析了旋转雷诺数和进出口压比对预旋喷嘴流量系数的影响。实验结果表明：在两个腔内离心升压效应明显,预旋喷嘴出口气流对预旋腔内的气流压力和速度的影响要远大于接收孔出口气流对盖板腔的影响,压比和旋转雷诺数对喷嘴流量系数有较小的影响。     

一种TeGe基快速相变型可逆光记录介质的研究

研制出一种在晶化激光功率为4mW时晶化时间为180ns的可逆相变型光纪录介质。其擦写循环次数可达10~6次。分析了其快速晶化机理。     

Unsteady drag measurements for flow over a circular disk

对垂直于来流方向的圆盘进行非定常测力实验,研究上游二维干扰圆杆和圆盘绕流雷诺数(雷诺数范围为0.44×10⁵~2.74×10⁵)对圆盘阻力及其脉动特性的影响.实验结果表明,无论有无上游干扰,圆盘平均阻力系数均不随雷诺数改变.上游干扰圆杆在降低圆盘阻力系数的同时,使圆盘阻力脉动量增大,而且当圆盘绕流雷诺数大于1.84×10⁵时阻力脉动量的增幅将随雷诺数的加大而迅速增加.对圆盘阻力的频谱分析表明,在圆盘上游无干扰时,圆盘绕流形成的螺旋状涡引起的非轴对称波动频率(斯特劳哈尔数为0.135)为阻力脉动的主频.     

Comptonization efficiencies of the variability classes of GRS 1915 + 105

The Galactic microquasar GRS 1915 + 105 exhibits at least seventeen types of variability classes. Intra and inter class transitions are reported to be observed within seconds to hours. Since the observation was not continuous, these classes appeared to be exhibited in a random order. Our goal is to predict a sequence of these classes. In this paper, we compute the ratio of the photon counts obtained from the power-law component and the blackbody component of each class and call this ratio as the ‘Comptonizing efficiency’ (CE) of that class. We sequence the classes in the ascending order of CE and find that this sequence matches with a few class transitions observed by RXTE satellite and IXAE instruments on board IRS-P3. A change in CE corresponds to a change in the optical depth of the Compton cloud. Our result implies that the optical depth of the Compton cloud gradually rises as the variability class becomes harder.     

Radiation of accretion disks in quasars and galactic nuclei

The continuum spectra of accretion disks around supermassive Schvarzshild black hole are calculated for a set of accretion disk parameters. In every point of the disk surface the atmosphere is considered to be similar to the atmosphere of the star with the same values of the surface gravity and effective temperature. All important effects of general relativity affected the spectrum shape are taken into account.     

涡轮盘概率风险的评估方法

针对CCAR33.70条款对涡轮盘开展概率风险评估的要求,研究了响应面法在定义重点采样区间以及计算裂纹扩展寿命中的应用,给出了在蒙特卡洛模拟过程中应用响应面法定义失效域,缩短样本方差、提高抽样效率的方法.分析结果表明应用重点采样法可以极大地提高抽样效率.采用重点采样法获得的失效样本数与总样本数的比例高达94%,远大于传统的直接抽样法获得的失效样本数与总样本数的比例（仅为33%）.该方法可以在保证分析精度的条件下减少样本的数量.另外,应用响应面法拟合寿命近似方程,可以极大地缩减裂纹扩展寿命的计算时间:利用寿命近似方程开展104次随机抽样所花费的时间仅有2min,远低于应用传统寿命计算方法所花费的时间（288 min）.通过对寿命近似方程的寿命计算误差分析可以看出:最大计算误差仅有1.0%,计算结果与传统裂纹扩展寿命模型的计算结果吻合度高.该研究成果可以提高涡轮盘概率风险评估的效率.      

涡轮盘瞬态温度场的分析方法

本文首先分析一个简化涡化盘模型，得到了各边界条件参数如冷气和燃气温度，换热系数对其温度场计算精度影响大小的排列次序，据此，在原稳态工作的基础上，建立了直接利用发动机工作参数计算和分析涡轮盘瞬态温度场的原理和方法，编制了有限元计算程序，同时进行了实例验算，计算结果与实测相比，误差一般不大于１０％。