Velocity Modeling and Inversion Techniques for Locating Microseismic Events in Unconventional Reservoirs

A velocity model is an important factor influencing microseismic event locations. We re-view the velocity modeling and inversion techniques for locating microseismic events in exploration for unconvent...     

基于背景重建的高光谱图像异常检测

针对高光谱图像异常检测中背景信息与异常目标信息难以有效区分,背景预测精度不佳的问题,提出一种新的基于背景重建的高光谱图像异常检测算法。通过字典学习方法获取高光谱图像背景光谱字典,并利用该字典对待检测图像进行稀疏重建,得到预测背景图像。将预测背景图像与原始图像做差后得到残差图像,进而利用局部RX检测算法对残差图像进行遍历,实现异常目标检测。通过对真实高光谱图像场景进行实验,证明了算法的有效性。     

电力二次系统安全防护综合仿真试验床研究

分析比较了现有的信息与网络安全仿真模型,指出各自模型的适用性和局限性.在以往主要针对局部对象进行安全仿真的研究基础上,结合电力二次系统整体安全防护需求,综合运用8种仿真技术和方案,设计实现了基于4个仿真层次,17个种类仿真试验的信息安全综合仿真试验床,实现针对电力信息系统的大型、分布式、联动式的综合信息安全仿真.使用证明,试验床能够为电力信息系统安全防护工程设计和实施提供多方位的仿真测试和评估依据.     

Influence of γ' precipitate on deformation and fracture during creep in PM nickel-based superalloy

FGH96 is a powder metallurgy nickel based superally used for turbine disk of aero-engines. In the present study FGH96 alloy with four different γ' precipitate microstructures were produced via solution heat-treatment with different cooling rates, and the maximum cooling rate reached 400°C/min which was a super cooling rate for Nickel-based superalloy. The creep tests were conducted for PM FGH96 alloy under the testing condition of 704°C and 690 MPa. The relationship between the creep properties and the distribution of γ' precipitate was established. The creep mechanism was analyzed by using TEM and ACTEM, and the dislocation movement was studied at the atomic scale. The creep strain rate was calculated through a physically based crystal slip model established based on crystal plasticity. The calculated results were consistent with the test ones, illustrating the validity of the model. The fracture mechanism was also investigated, and the results showed that the creep cracks generated on the surface due to the oxidation. It was observed that the cracks propagated in different ways depending on the different average diameters of γ' precipitate. With the decrease of the average γ' precipitate size,the critical shearing stress increased and the resistance of the dislocation slipping increased. The fracture mechanism for the primary stage transformed from intragranular to intergranular due to the change of dislocation slipping.     

Effect of cooling rate during quenching on the microstructure and creep property of nickel-based superalloy FGH96

The effect of cooling rate during quenching on the microstructure and creep property of nickel-based superalloy FGH96 was investigated. Three groups of samples were quenched continuously with three fixed cooling rates, respectively, then subjected to a creep test under a constant load of 690 MPa at 700℃. Clear differences in size of secondary γ′ precipitates, creep properties and substructure of creep-tested samples were observed. The quantitative relationship among cooling rate, the size of secondary γ′ precipitates, and steady creep rate was constructed. It was found that with increasing cooling rate, the size of secondary γ′ precipitates decreases gradually, showing that the relationship between the size of secondary γ′ precipitates and the cooling rate obeys a power law, with an exponent of about –0.6, and the creep rate of steady state follows a good parabola relationship with cooling γ′ precipitate size. For 235℃/min, FGH96 alloy exhibited very small steady creep rate. The density of dislocation was low, and the isolated stacking fault was the dominant deformation mechanism. With decreasing cooling rates, the density of dislocation increased remarkably, and deformation microtwinning was the dominant deformation process. Detailed mechanisms for different cooling rate were discussed.     

成核改性对聚乳酸结晶行为的影响

选用PPA-Zn、TMC-328和TMP-3000为成核剂(NA),分别与聚乳酸(PLA)熔融共混,改性制备成PLA/NA复合材料,通过差示扫描量热分析、偏光显微观察、X射线衍射、动态热力学分析和热变形温度测试研究PLA/NA材料的结晶行为、动态热力学性能和耐热性能。结果表明,3种成核剂中,PPA-Zn和TMC-328更能提高PLA结晶度、储能模量和热变形温度,PLA/PPA-Zn和PLA/TMC-328半结晶时间分别为0.27min和0.28min,晶体形貌分别为针状晶和枝状晶,为α晶型,初始储能模量分别为3.921GPa和4.486GPa,110℃退火60s结晶后的热变形温度分为127.1℃和121.1℃。     

不同铸造方法对船用螺旋桨毂成型质量的影响

采用ZCuAl9Fe4Ni4Mn2铝青铜合金为结构材料,研究3种不同铸造方法对船用桨毂组织性能的影响。结果表明,重力铸造桨毂窗口下方有大量氧化夹渣存在;低压铸造容易获得组织致密、性能优良的桨毂,但工序较多;离心铸造可获得较为致密的桨毂断面组织,二次氧化夹渣状况较重力铸造得到明显改善,但离心转速超过150r/min时,容易产生缩孔和缩松。     

喷泉码在多接口无线多媒体传输中的应用

讨论了一种GF(m)随机线性喷泉码及其译码的在线高斯消元算法,分析了其译码开销和译码复杂度,并给出了其参数选取方案。为了论证该方案的有效性,对应用该方案的多接口无线多媒体传输系统进行了测试分析,测试结果表明,该方案的系统传输速率和可靠性都接近最优。