Asymptotics of the Far Fields of Internal Gravity Waves Excited by a Source of Radial Symmetry

Abstract— The problem of the far field of internal gravity waves generated by a perturbation source of radial symmetry aroused at an initial instant of time is solved. The constant model distribution of the buoyancy frequency is considered and, using the Fourier–Hankel transform, an analytical solution to the problem is obtained in the form of the sum of wave modes. Asymptotics of the solutions that describe the spatial-temporal characteristics of elevation of the isopycnic lines and the vertical and horizontal velocity components far from the perturbation source are obtained. The asymptotics of the components of the wave field are expressed in terms of the square of the Airy function and its derivatives in the neighborhood of the wave fronts of an individual wave mode. The exact and asymptotic results are compared and it is shown that the asymptotic method makes it possible to calculate effectively the far wave fields at times of the order of ten and more of the Brunt–Väisälä periods.

Accurate Online Battery Impedance Measurement Method with Low Output Voltage Ripples on Power Converters

The conventional online battery impedance measurement method works by perturbing the duty cycle of the DC-DC power converter and measuring the response of the battery voltage and current. This periodical duty cycle perturbation will continuously generate large voltage ripples at the output of power converters. These large ripples will not easily be removed due to the high amplitude and wide frequency range and would be a challenge to meet tight output regulation. To solve this problem, this paper presents a new online battery impedance measurement technique by inserting a small switched resistor circuit (SRC) into the converter. The first contribution of this work is that the perturbation source is moved from the main switch to the input-side of the converter, so the ripples are reduced. The analysis and experimental results of the proposed method show a reduction of 16-times compared with the conventional method. The second contribution tackles the possible change of the battery state of charge (SOC) during the online battery measurement process, which will inevitably influence the impedance measurement accuracy. In this proposed method, battery impedance at multiple frequencies can be measured simultaneously using only one perturbation to accelerate measurement speed and minimize possible SOC change. The experimental impedance results coincide with a high-accuracy laboratory battery impedance analyzer.

State of stress in central and eastern North American seismic zones

We use a Bayesian analysis to determine the state of stress from focal mechanisms in ten seismic zones in central and eastern North America and compare it with regional stress inferred from borehole measurements. Comparisons of the seismologically determined azimuth of the maximum horizontal compressive stress (S HS ) with that determined from boreholes (S HB ) exhibit a bimodal pattern: In four zones, the S HS and regional S HB orientations are closely parallel, whereas in the Charlevoix, Lower St. Lawrence, and Central Virginia zones, the S HS azimuth shows a statistically significant 30°-50° clockwise rotation relative to the regional S HB azimuth. This pattern is exemplified by the northwest and southeast seismicity clusters in Charlevoix, which yield S HS orientations strictly parallel and strongly oblique, respectively, to the regional S HB trend. Similar ~30° clockwise rotations are found for the North Appalachian zone and for the 2003 Bardwell earthquake sequence north of the New Madrid zone. The S HB /S HS rotations occur over 20-100 km in each seismic zone, but they are observed in zones separated by distances of up to 1500 km. A possible mechanism for the stress rotations may be the interaction between a long-wavelength stress perturbation source, such as postglacial rebound, and local stress concentrators, such as low-friction faults. The latter would allow low-magnitude (<10 MPa) postglacial rebound stresses to locally perturb the preexisting stress field in some seismic zones, whereas postglacial rebound stresses have little effect on the intraplate state of stress in general. © 2010 Geological Society of America.

State of stress in central and eastern North American seismic zones

We use a Bayesian analysis to determine the state of stress from focal mechanisms in ten seismic zones in central and eastern North America and compare it with regional stress inferred from borehole measurements. Comparisons of the seismologically determined azimuth of the maximum horizontal compressive stress (S HS ) with that determined from boreholes (S HB ) exhibit a bimodal pattern: In four zones, the S HS and regional S HB orientations are closely parallel, whereas in the Charlevoix, Lower St. Lawrence, and Central Virginia zones, the S HS azimuth shows a statistically significant 30°-50° clockwise rotation relative to the regional S HB azimuth. This pattern is exemplified by the northwest and southeast seismicity clusters in Charlevoix, which yield S HS orientations strictly parallel and strongly oblique, respectively, to the regional S HB trend. Similar ~30° clockwise rotations are found for the North Appalachian zone and for the 2003 Bardwell earthquake sequence north of the New Madrid zone. The S HB /S HS rotations occur over 20-100 km in each seismic zone, but they are observed in zones separated by distances of up to 1500 km. A possible mechanism for the stress rotations may be the interaction between a long-wavelength stress perturbation source, such as postglacial rebound, and local stress concentrators, such as low-friction faults. The latter would allow low-magnitude (<10 MPa) postglacial rebound stresses to locally perturb the preexisting stress field in some seismic zones, whereas postglacial rebound stresses have little effect on the intraplate state of stress in general. © 2010 Geological Society of America.

Tidal generated electric field in the multi-layer structure and the possibilities of its employment for deriving the elastic properties and permeability of the subsurface formations

An analytical solution of pore pressure equations with a perturbation source in the form of lunar-solar tidal deformations is generalized to the case of a model with the arbitrary number of layers. The electric field of electrokinetic nature is calculated. The sensitivity of pore pressure and its vertical derivative to the elastic properties and permeability of rock strata is evaluated. The program code for solving the inverse problem capable of recovering the Biot modulus and Biot coefficient as well as permeability coefficient in a horizontally layered model is developed. The possibilities of mapping these parameters are discussed including their study from the borehole measurements of the vertical electric field of electrokinetic origin.

MSF: Modulated Sub-graph Finder

High throughput techniques such as RNA-seq or microarray analysis have proven to be invaluable for the characterization of global transcriptional gene activity changes due to external stimuli or diseases. Differential gene expression analysis (DGEA) is the first step in the course of data interpretation, typically producing lists of dozens to thousands of differentially expressed genes. To further guide the interpretation of these lists, different pathway analysis approaches have been developed. These tools typically rely on the classification of genes into sets of genes, such as pathways, based on the interactions between the genes and their function in a common biological process. Regardless of technical differences, these methods do not properly account for cross talk between different pathways and rely on binary separation into differentially expressed gene and unaffected genes based on an arbitrarily set p-value cut-off. To overcome this limitation, we developed a novel approach to identify concertedly modulated sub-graphs in the global cell signaling network, based on the DGEA results of all genes tested. Thereby, expression patterns of genes are integrated according to the topology of their interactions and allow potentially to read the flow of information from the perturbation source to the effectors. The described software, named Modulated Sub-graph Finder (MSF) is freely available at https: //github.com/Modulated-Subgraph-Finder/MSF.