Near-Surface Interface Detection for Coal Mining Applications Using Bispectral Features and GPR

The use of ground penetrating radar (GPR) for detecting the presence of near-surface interfaces is a scenario of special interest to the underground coal mining industry. The problem is difficult to solve in practice because the radar echo from the near-surface interface is often dominated by unwanted components such as antenna crosstalk and ringing, ground-bounce effects, clutter, and severe attenuation. These nuisance components are also highly sensitive to subtle variations in ground conditions, rendering the application of standard signal pre-processing techniques such as background subtraction largely ineffective in the unsupervised case. As a solution to this detection problem, we develop a novel pattern recognition-based algorithm which utilizes a neural network to classify features derived from the bispectrum of 1D early time radar data. The binary classifier is used to decide between two key cases, namely whether an interface is within, for example, 5 cm of the surface or not. This go/no-go detection capability is highly valuable for underground coal mining operations, such as longwall mining, where the need to leave a remnant coal section is essential for geological stability. The classifier was trained and tested using real GPR data with ground truth measurements. The real data was acquired from a testbed with coal-clay, coal-shale and shale-clay interfaces, which represents a test mine site. We show that, unlike traditional second order correlation based methods such as matched filtering which can fail even in known conditions, the new method reliably allows the detection of interfaces using GPR to be applied in the near-surface region. In this work, we are not addressing the problem of depth estimation, rather confining ourselves to detecting an interface within a particular depth range

Selective Mixed Tishchenko Reaction via Substituted 4-Hydroxy-1,3-Dioxanes

Monoesters of 1,3-diols can be prepared with the mixed Tishchenko reaction from â-hydroxy aldehydes and another aldehyde. These two aldehydes form a diastereomeric mixture of 1,3-dioxan-4-ol hemiacetal derivatives which can be further converted to monoesters with suitable catalysts. Limitations in the formation and esterification of this hemiacetal intermediate have been investigated in this work and the formation and stability of 1,3-dioxan-4-ols was found to be aldehyde-, temperature-, and solvent-dependent. A new method was developed for selective preparation of monoesters of 1,3-diols with this mixed Tishchenko reaction via 1,3-dioxan-4-ols without any significant side products. During the development of this method a possibility to scale up the reactions to reach a selective and economical process was one of the main targets in this work.Peer reviewe

Mono-, di- and tri-nuclear Ni(II) complexes of N-, O-donor ligands: structural diversity and reactivity

A series of mono-, di- and tri-nuclear Ni(II) complexes of N, O-donating molecules possessing ---H2C---NH--- and ---HC=N--- moieties have been synthesized and characterized and the structures have been determined by single crystal X-ray diffraction. All these exhibited interesting molecular packing in their crystal lattices. Di-nuclear complexes were found to be cleaved in pyridine to result in mononuclear ones with additional coordinations being provided by pyridine. Di-nuclear complexes were found to form urea adducts as demonstrated based on absorption and vibrational studies.© Elsevie

Synthesis, structural diversity, inter-conversion and reactivity of Cu(II) complexes of hydroxy-rich molecules

Tetranuclear Cu(II) complexes having linear, cubane and pseudodouble-cubane cores were synthesized using hydroxy-rich molecules possessing amine and imine groups. The products were structurally characterized and were studied for their ability to oxidize catechol as well as for their inter-conversion between mono- and tetra-nuclear complexes