Improved Gabor Deconvolution and Its Extended Applications

In log time-frequency spectra, the nonstationary convolution model is a linear equation and thus we improved the Gabor deconvolution by employing a log hyperbolic smoothing scheme which can be implemented as an iteration process. Numerical tests and practical applications demonstrate that improved Gabor deconvolution can further broaden frequency bandwidth with less computational expenses than the ordinary method. Moreover, we attempt to enlarge this method’s application value by addressing nonstationary and evaluating Q values. In fact, energy relationship of each hyperbolic bin (i.e., attenuation curve) can be taken as a quantitative indicator in balancing nonstationarity and conditioning seismic traces to the assumption of unchanging wavelet, which resultantly reveals more useful information for constrained reflectivity inversion. Meanwhile, a statistical method on Q-value estimation is also proposed by utilizing this linear model’s gradient. In practice, not only estimations well agree with geologic settings, but also applications on Q-compensation migration are favorable in characterizing deep geologic structures, such as the pinch-out boundary and water channel.     

Holocene records of eolian dust deposition from high-elevation lakes in the Uinta Mountains,Utah, USA

Radiocarbon-dated sediment cores from subalpine lakes were used to investigate post-glacial dust deposition in the Uinta Mountains (Utah, USA). Lake sediments were geochemically characterized with ICP-OES, ICP-MS and XRF core scanning. Collections from passive samplers constrain the properties of modern dust, and samples of regolith constrain properties of the local material within the watershed. Ca and Eu are more abundant in dust, whereas Ti and Zr are more abundant in local regolith. As a result, the Ca/Ti and Eu/Zr ratios are indices for the dust content of lake sediment. In all records, the dust index rises in the early Holocene as watersheds became stabilized with vegetation, reducing the influx of local material. After this point, values remained above average through the middle Holocene, consistent with an increased dust content in the sediment. Dust index values drop in the late Holocene in most lakes, suggesting a decrease in dust abundance. Generally synchronous shifts in dust index values in cores from lakes in different parts of this mountain range are evidence of enhanced dust deposition in this region during the middle Holocene, and are consistent with a variety of records for increased aridity in the south-western USA at this time.     

Inducing fractures and increasing cleat apertures in a bituminous coal under isotropic stress via application of microwave energy

For the degassing of coal seams, either prior to mining or in un-minable seams to obtain coalbed methane, it is the combination of cleat frequency, aperture, connectivity, stress, and mineral occlusions that control permeability. Unfortunately, many potential coalbeds have limited permeability and are thus marginal for economic methane extraction. Enhanced coalbed methane production, with concurrent CO₂ sequestration is also challenging due to limited CO₂ injectivity. Microwave energy can, in the absence of confining stress, induce fractures in coal. Here, creation of new fractures and increasing existing cleat apertures via short burst, high-energy microwave energy was evaluated for an isotropically stressed and an unstressed bituminous coal core. A microwave-transparent argon gas pressurized (1000 psi) polycarbonate vessel was constructed to apply isotropic stress simulating ~ 1800 foot depth. Cleat frequency and distribution was determined for the two cores via micro-focused X-ray computed tomography. Evaluation occurred before and after microwave exposure with and without the application of isotropic stress during exposure. Optical microscopy was performed for tomography cleat aperture calibration and also to examine lithotypes influences on fracture: initiation, propagation, frequency, and orientation. It was confirmed that new fractures are induced via high-energy microwave exposure in an unconfined bituminous core and that the aperture increased in existing cleats. Cleat/fracture volume, following microwave exposure increased from 1.8% to 16.1% of the unconfined core volume. For the first time, similar observations of fracture generation and aperture enhancement in coal were also determined for microwave exposure under isotropic stress conditions. An existing cleat aperture, determined from calibrated X-ray computed tomography increased from 0.17 mm to 0.32 mm. The cleat/fracture volume increased from 0.5% to 5.5%. Optical microscopy indicated that fracture initiated likely occurred in at least some cases at fusain microlithotypes. Presumably this was due to the open pore volumes and potential for bulk water presence or steam pressure buildup in these locations. For the major induced fractures, they were mostly horizontal (parallel to the bedding plane) and often contained within lithotype bands. Thus it appears likely that microwaves have the potential to enhance the communication between horizontal wellbore and existing cleat network, in coal seams at depth, for improved gas recovery or CO₂ injection.     

A high speed photometer in the optical region for lunar occultation studies

High speed photometry during the lunar occultation of a stellar system provides an effective means of achieving high angular resolution in one dimension at the sub arc second level which is well suited for resolving close binary projected separations in the range of 10–100 milliarc seconds. An optical fast photometer designed for such a purpose is described and some results from the initial observations taken with the system including the resolution of a projected separation of 55 milli arcsecond in one binary system are detailed.     

COMPUTATIONAL SIMULATION OF RIVER SEDIMENTATION AND MORPHOLOGY - A REVIEW OF THE STATE OF THE ART

In this paper, the state-of-the-art computational simulation technologies for river sedimentation and morphology are comprehensively reviewed. Emphasis is on computational modelling, which includes mathematical modelling equations and closures, numerical solution methods, verification and validation, model integration, and applications. Several important areas of future research are recommended.     

Machine learning innovations in address matching: A practical comparison of word2vec and CRFs

Record linkage is a frequent obstacle to unlocking the benefits of integrated (spatial) data sources. In the absence of unique identifiers to directly join records, practitioners often rely on text‐based approaches for resolving candidate pairs of records to a match. In geographic information science, spatial record linkage is a form of geocoding that pertains to the resolution of text‐based linkage between pairs of addresses into matches and non‐matches. These approaches link text‐based address sequences, integrating sources of data that would otherwise remain in isolation. While recent innovations in machine learning have been introduced in the wider record linkage literature, there is significant potential to apply machine learning to the address matching sub‐field of geographic information science. As a response, this paper introduces two recent developments in text‐based machine learning—conditional random fields and word2vec—that have not been applied to address matching, evaluating their comparative strengths and drawbacks.     

ANTHROPOGENIC GEOMORPHOLOGY IN NORTHERN ALASKA

Two classes of anthropogenic landforms can be recognized in the permafrost environment of northern Alaska. Primary anthropogenic landforms result from the operation of natural geomorphic processes on man-made features such as roads or gravel berms. Secondary anthropogenic forms are identical to natural geomorphic features, but evolve as indirect consequences of human actions. The first group is illustrated by a badly thermokarsted road, which has caused serious drainage disruptions likely to persist over a long time period. Secondary forms are exemplified by fields of palsa-like features, which are common where pipeline-related construction activities or structures cause shallow ponding. Because they evolve rapidly, anthropogenic permafrost landforms can provide great insight into the development of natural periglacial features.