In this paper, a finite element approach is applied to study the dispersion properties of non-leaky acoustic waves inside boreholes with off-centered LWD (logging while drilling) tools. Both soft and hard formation cases are studied with focus on phase velocity dispersions of Stoneley, dipole and quadrupole modes. When an LWD tool is off-centered, the dispersion curve of the Stoneley mode shift...

leaf wetness duration (lwd) is a key parameter in agricultural meteorology. because of difficulties involved in lwd being readily measured, several methods have been developed to estimate it from weather data. among the employed to estimate lwd, those that use physical principles of dew formation plus dew and/or rain evaporation have shown to be especially transmittable and of sufficiently accu...

PURPOSE We determined the feasibility of fovea and optic nerve head imaging with a long working distance (LWD) swept source optical coherence tomography (OCT) prototype in adults, teenagers, and young children. METHODS A prototype swept source OCT system with a LWD (defined as distance from the last optical element of the imaging system to the eye) of 350 mm with custom fixation targets was d...

We present new results both from numerical simulations using the Swift–Hohenberg model and from experiment for domain chaos near the onset of rotating Rayleigh–Bénard convection. Using both global Fourier analysis and local wave director (LWD) analysis, the domain chaos patterns were characterized. Several image analysis techniques are discussed and were applied to the director field obtained f...

There has been limited research on the breakdown, recycling, and flux of carbon from large woody detritus (LWD) in mangrove forests. The breakdown LWD is caused by guilds terrestrial marine biodegrading organisms that degrade wood at a range rates efficiencies. Spatial variations environmental factors within mangroves affect distribution community organisms, which, turn, impacts flow sequestrat...

Among the best structures for implementing recursive digital filters are lattice wave digital (LWD) filters (parallel connections of all-pass filters). They are characterized by many attractive properties, such as a reasonably low coefficient sensitivity, a low roundoff noise level, and the absence of parasitic oscillations. This book chapter describes an efficient algorithm for the design of m...

We present an application of the two-and-half dimensional (2.5D) multiplicative-regularized Gauss-Newton inversion method for the interpretation of the directional resistivity measurements [electromagnetic logging-while-drilling (LWD) measurements]. In this work, an inversion algorithm is employed for obtaining a two-dimensional (2D) resistivity distribution (pixel-based) of the subsurface. Sev...

Formation anisotropic constants play an important role in the determination of formation stresses, fractures, lithology, and mechanical properties. These characteristics provide critical inputs to wellbore stability during drilling optimal completion designs hydrocarbon bearing reservoirs. However, there are no available techniques for estimation a sub-set using Logging-While-Drilling (LWD) son...

Natural flood management interventions, such as Large Wood Debris (LWD) or engineered log jams, are being increasingly deployed throughout the UK and elsewhere. In addition to alleviating risk, it is anticipated that they may influence ecology of freshwater river systems, including macroinvertebrate populations. This study explores assemblages, water quality parameters, sediment size distributi...