Let T be an operator on a separable Hilbert space H and T = U｜T｜ be the polar decomposition. T is said to be log-ω-hyponormal if log ｜~T｜ ≥ log｜T｜≥ log ｜~T^＊｜. In this paper we prove that the point spectru...Let T be an operator on a separable Hilbert space H and T = U｜T｜ be the polar decomposition. T is said to be log-ω-hyponormal if log ｜~T｜ ≥ log｜T｜≥ log ｜~T^＊｜. In this paper we prove that the point spectrum of T is equal to its joint point spectrum if T is log-ω-hyponormal. We also prove that a log-ω-hyponormal operator is normaloid, i.e., r（T） =｜｜T｜｜. Finally, we obtain Putnam＇s theorem for log-ω-hyponormal operators.展开更多
Sedimentary cyclothems at different scales show formations’ fractal structure which can be reflected on logs. The slope of the power spectrum of log is related to the fractal dimension of formations. The fractal dime...Sedimentary cyclothems at different scales show formations’ fractal structure which can be reflected on logs. The slope of the power spectrum of log is related to the fractal dimension of formations. The fractal dimensions from two logs with similar vertical resolutions are the same. Using fractal interpolating algorithm density log can be reconstructed. The reconstructed log can be compared with core density in washout intervals.展开更多
Nuclear Magnetic Resonance mud logging technology (NMR mud logging) is a new mud logging technology. Mainly applies the CPMG(Carr-Purcell-Meiboom-Gill)pulse sequence to measure transverse relaxation time (T2) of the f...Nuclear Magnetic Resonance mud logging technology (NMR mud logging) is a new mud logging technology. Mainly applies the CPMG(Carr-Purcell-Meiboom-Gill)pulse sequence to measure transverse relaxation time (T2) of the fluid. NMR mud logging can measure drill cutting, core and sidewall core in the well site, also according to the experiment results, the sample type and size has little effect to analysis result. Through NMR logging, we can obtain several petrophysical parameters such as total porosity, effective porosity, permeability, oil saturation, water saturation, movable fluid saturation, movable oil saturation, movable water saturation, irreducible fluid saturation, irreducible oil saturation, irreducible water saturation, pore size and distribution in rock samples, etc. NMR mud logging has been used nearly 10 years in China, Sudan, Kazakhstan, etc. it plays an important role in the interpretation and evaluation of reservoir and its fluids.展开更多
变转速工况下,转速变化会导致不同时间段峭度值出现变化,且高脉冲噪声会导致振动信号的峭度值突然变大。这些因素削弱了快速谱峭度图(Fast kurtogram,简称FK)方法提取微弱故障特征方面的性能,为了克服这些缺陷,提出一种基于对数平方包...变转速工况下,转速变化会导致不同时间段峭度值出现变化,且高脉冲噪声会导致振动信号的峭度值突然变大。这些因素削弱了快速谱峭度图(Fast kurtogram,简称FK)方法提取微弱故障特征方面的性能,为了克服这些缺陷,提出一种基于对数平方包络谱的新特征--对数包络阶次循环分量(Log-envelope Order Cyclic Content,简称LEOC),构造出一种对数包络阶次循环分量图(Log-envelope Order Cycligram,简称LEOCgram)。首先使用1/3二叉树结构对原始信号进行多层次滤波,并计算每一组滤波子信号的平方包络。然后,通过计算阶次跟踪(Computed Order Tracking,简称COT)技术对每一组的平方包络序列进行角域重采样,计算每一组滤波信号的对数平方包络谱并进行自相关分析得到可能的故障特征阶。最后计算LEOC值,LEOC最大值对应的频带即为最优解调频带。将最优解调频带作为滤波器的参数对原始信号进行滤波,通过对滤波后的信号进行包络阶次分析并根据包络阶次谱的阶次结构可以确定故障类型。仿真信号和试验轴承外圈故障信号的分析结果表明,该方法在速度波动范围较大时,能够准确地对滚动轴承故障进行诊断,且不受随机高脉冲噪声的影响。展开更多
文摘Let T be an operator on a separable Hilbert space H and T = U｜T｜ be the polar decomposition. T is said to be log-ω-hyponormal if log ｜~T｜ ≥ log｜T｜≥ log ｜~T^＊｜. In this paper we prove that the point spectrum of T is equal to its joint point spectrum if T is log-ω-hyponormal. We also prove that a log-ω-hyponormal operator is normaloid, i.e., r（T） =｜｜T｜｜. Finally, we obtain Putnam＇s theorem for log-ω-hyponormal operators.
文摘Sedimentary cyclothems at different scales show formations’ fractal structure which can be reflected on logs. The slope of the power spectrum of log is related to the fractal dimension of formations. The fractal dimensions from two logs with similar vertical resolutions are the same. Using fractal interpolating algorithm density log can be reconstructed. The reconstructed log can be compared with core density in washout intervals.
文摘Nuclear Magnetic Resonance mud logging technology (NMR mud logging) is a new mud logging technology. Mainly applies the CPMG(Carr-Purcell-Meiboom-Gill)pulse sequence to measure transverse relaxation time (T2) of the fluid. NMR mud logging can measure drill cutting, core and sidewall core in the well site, also according to the experiment results, the sample type and size has little effect to analysis result. Through NMR logging, we can obtain several petrophysical parameters such as total porosity, effective porosity, permeability, oil saturation, water saturation, movable fluid saturation, movable oil saturation, movable water saturation, irreducible fluid saturation, irreducible oil saturation, irreducible water saturation, pore size and distribution in rock samples, etc. NMR mud logging has been used nearly 10 years in China, Sudan, Kazakhstan, etc. it plays an important role in the interpretation and evaluation of reservoir and its fluids.
文摘变转速工况下,转速变化会导致不同时间段峭度值出现变化,且高脉冲噪声会导致振动信号的峭度值突然变大。这些因素削弱了快速谱峭度图(Fast kurtogram,简称FK)方法提取微弱故障特征方面的性能,为了克服这些缺陷,提出一种基于对数平方包络谱的新特征--对数包络阶次循环分量(Log-envelope Order Cyclic Content,简称LEOC),构造出一种对数包络阶次循环分量图(Log-envelope Order Cycligram,简称LEOCgram)。首先使用1/3二叉树结构对原始信号进行多层次滤波,并计算每一组滤波子信号的平方包络。然后,通过计算阶次跟踪(Computed Order Tracking,简称COT)技术对每一组的平方包络序列进行角域重采样,计算每一组滤波信号的对数平方包络谱并进行自相关分析得到可能的故障特征阶。最后计算LEOC值,LEOC最大值对应的频带即为最优解调频带。将最优解调频带作为滤波器的参数对原始信号进行滤波,通过对滤波后的信号进行包络阶次分析并根据包络阶次谱的阶次结构可以确定故障类型。仿真信号和试验轴承外圈故障信号的分析结果表明,该方法在速度波动范围较大时,能够准确地对滚动轴承故障进行诊断,且不受随机高脉冲噪声的影响。
