An accurate analytical approach to electron crystallography

A much more accurate analytical expression of dynamical electron diffraction than the phase object approximation (POA) formula has been derived in this paper which decreases the restriction of sample thickness up to almost one order of magnitude compared to POA theory. The importance of the new expression is twofold. First, a sample with such a thickness that new expression remains valid can be prepared experimentally. Second, the new expression reveals a clear and straightforward relationship between the wave function and crystal potential. In the expression, the effect of dynamical diffraction on wave function can be simply attributed to two factors TP(D) = (sin(lambda pi zg2))/(4pi2g2) and TA(D) = [1 - cos(lambda pi zg2)]/4pi2g2. Compared to the effect of transfer functions of an electron microscope on wave function, we found that TP(d) and TA(d) play the same role as transfer function but are independent of the instrument.For this reason, we here call the former as "extrinsic transfer functions" and the latter as "intrinsic" ones. In principle, one should correct not only extrinsic transfer functions but also intrinsic ones if one desires to achieve higher resolution.     

The influence of bitumen on reservoir properties and hydrocarbon accumulation in the Santai Area of the Junggar Basin,North Western China

Bitumen's influence on reservoir properties and hydrocarbon accumulation in Santai area was studied by experiment measures and geochemical evidences. The porosity and permeability of the sandstones containing bitumen increased significantly by dissolving experiments, implying that bitumen strongly influences the reservoir properties. The analysis reveals that there were two stages of hydrocarbon accumulation. In the first stage oil migrated into coarse-grained sandstone and then degraded to bitumen, which deteriorated the reservoir properties. The second stage oil had to migrate into fine-grained sandstones, or the residual pores of the bitumen-containing coarse-grained sandstone. Exploration in this area should avoid the bitumen distribution zone.     

Counter-example to ‘Sufficient and necessary condition for the asymptotic stability of discrete linear interval systems’

In Jiang (1988), a condition is given which is supposedly necessary and sufficient for the stability of interval matrices in discrete-time systems. We demonstrate, via a counter-example, that the condition given is, in fact, not sufficient.     

Detection of cross-channel anomalies

The data deluge has created a great challenge for data mining applications wherein the rare topics of interest are often buried in the flood of major headlines. We identify and formulate a novel problem: cross-channel anomaly detection from multiple data channels. Cross-channel anomalies are common among the individual channel anomalies and are often portent of significant events. Central to this new problem is a development of theoretical foundation and methodology. Using the spectral approach, we propose a two-stage detection method: anomaly detection at a single-channel level, followed by the detection of cross-channel anomalies from the amalgamation of single-channel anomalies. We also derive the extension of the proposed detection method to an online settings, which automatically adapts to changes in the data over time at low computational complexity using incremental algorithms. Our mathematical analysis shows that our method is likely to reduce the false alarm rate by establishing theoretical results on the reduction of an impurity index. We demonstrate our method in two applications: document understanding with multiple text corpora and detection of repeated anomalies in large-scale video surveillance. The experimental results consistently demonstrate the superior performance of our method compared with related state-of-art methods, including the one-class SVM and principal component pursuit. In addition, our framework can be deployed in a decentralized manner, lending itself for large-scale data stream analysis.     

Wide Gap TLP Bonding a Single-Crystal Superalloy: Evolution of the L/S Interface Morphology and Formation of the Isolated Grain Boundaries

The microstructural evolution and bonding behavior of transient liquid phase (TLP) bonded joints for single-crystal superalloy samples with a 300-μm-wide gap have been investigated. The results show that at the initial stage, the interface grows with a cellular structure. With the increase of time, the length and numbers of the cellular structures decrease. At the final stage, the interface evolves with a planar manner. The gradient of B ahead of the liquid/solid interface exists and becomes sharper from the initial to the final analyzed from the electron probe microanalysis (EPMA) results. Inevitably, isolated grain forms during the evolution of the interface and the growth rate of isothermal solidification zone (ISZ) changes through the whole bonding process, and these both deviate from the traditional TLP bonding models. The mechanisms of the formation of the isolated grain boundaries and the reasons for the deviation of the solidification rate are discussed. Also, some effective methods to avoid the formation of isolated grain boundaries in the ISZ are proposed.