Optimization of Subsurface Flow Operations Using a Dynamic Proxy Strategy

Mathematical Geosciences - Machine-learning-based proxy models are often used to replace many of the flow simulations required in optimizations of subsurface flow processes. Because the optimizer...     

iGeoTrans – a novel iOS application for GPS positioning in geosciences

The iGeoTrans is an iOS application designed for navigation purposes for iPhone, iPad and iPod Touch. This application uses Global Positioning System (GPS), Assisted GPS system, GLONASS, Wi-Fi and Cellular Network for positioning. The iGeoTrans has included datum transformations and map projections that enable users to convert the collected data between different coordinate systems for almost all areas in the world. In addition, other features are also included such as distance, area measurements, and GPS results could be exported to the AutoCad dxf format for GIS softwares. The average horizontal and vertical root mean square errors (RMSEs) for the static test are around 4.11 and 3.51?m, respectively. The horizontal RMSE for the dynamic outdoor test is around 2.72?m. The iGeoTrans application can be used to support surveying, mapping and geosciences fieldworks for any area in the world.     

Different Borders‐Different Cooperation? Transborder Cooperation in Poland

The aim of this paper was to analyze the role of border and borderland type in transborder cooperation. To this end, 591 projects under six Interreg IIIA Programs in which Polish border regions participated from 2004 to 2006 were examined. These programs were compared to identify the various factors influencing projects in different border regions. Although research on cooperation usually focuses on a national scale, actual cooperation depends largely on regional and local conditions, which are the focus of this study. Despite a common legal and institutional framework, the Interreg projects were not all realized in the same way. Different local conditions had impacts on programs and implementation. Therefore, the effectiveness and achievement of transborder cooperation objectives depended on the modification of each program to specific regional conditions.     

Radio Observation of Solar-Activity-Related mHz Oscillations

The VATLY radio telescope, operating at 1.415 GHz in Ha Noi, has been used to track the Sun in the summer?–?autumn months in 2012. Evidence has been obtained for solar activity, including occasional flares and variable oscillations with amplitudes at the percent level and periods of about 6 min. Comparison with data collected at the same frequency by the Learmonth Observatory in Australia suggests that the observed oscillations were associated with solar activity. A joint analysis of both data sets is presented, evaluating the correlations between them. We describe the common and different main features.     

Effective transfer properties of partially saturated geomaterials with interfaces using the immersed interface method

The present work aims at introducing an efficient numerical approach based on the immersed interface method to estimate the effective thermal conductivity and permeability of geomaterials as porous media with either perfect or debonded interfaces. The first part deals with the problem of the overall thermal properties of a medium containing perfectly bonded inclusions. The evolution of the homogenized properties with respect to the properties of individual constituents, the volume fraction, the spatial distribution, and the shape of inclusions is highlighted. The second part of the paper is devoted to the case of imperfectly bonded inclusions. An extension of the immersed interface method in this context makes it possible to study other aspects that have an influence on the effective properties such as the interfacial resistance and the size of inclusions. The application of the proposed numerical tool to some porous rocks in partially saturated condition shows good agreement with the available experimental results and demonstrates the performance and the flexibility of the developed procedure.Copyright © 2013 John Wiley & Sons, Ltd.     

Nonlinear control of an active heave compensation system

Heave motion of a vessel or a rig has an adverse impact on the response of a drill-string or a riser. To compensate for heave motion, passive and active devices are usually used. Active heave compensators, in which a control system is an essential part, allow conducting operations under more extreme weather conditions than passive ones. This paper presents a constructive method to design a nonlinear controller for an active heave compensation system using an electro-hydraulic system driven by a double rod actuator. The control system reduces the effect of the heave motion of the vessel on the response of the riser by regulating the distance from the upper end of the riser to the seabed. The control development is based on Lyapunov's direct method and disturbance observers. The paper also includes a method to select the control and disturbance observer gains such that actuator saturations are avoided. Stability of the closed loop system is carefully examined. Simulation results illustrate the effectiveness of the proposed control system.     

Faulting, mass-wasting and deposition in an active dextral shear zone, the Gulf of Saros and the NE Aegean Sea, NW Turkey

Structural, mass-wasting and sedimentation processes along an active dextral shear zone beneath the Gulf of Saros and the NE Aegean Sea were investigated on the basis of new high-resolution swath bathymetric data and multi-channel seismics. A long history of dextral shearing operating since the Pliocene culminated in the formation of a NE-SW-trending, ca. 800-m-deep basin (the so-called inner basin) in this region, which is bordered by a broad shelf along its northern and eastern sides and a narrow shelf at the southern side. The western extension of the North Anatolian Fault Zone (the Ganos Fault) cuts the eastern shelf along a narrow deformation zone, and ends sharply at the toe of the slope, where the strain is taken up by two NE-SW-oriented fault zones. These two fault zones cut the basin floor along its central axis and generate a new, Riedel-type pull-apart basin (the so-called inner depression). According to the bathymetric and seismic data, these basin boundary fault zones are very recent features. The northern boundary of the inner depression is a through-going fault comprising several NE-SW- and E-W-oriented, overlapping fault segments. The southern boundary fault zone, on the other hand, consists of spectacular en-echelon fault systems aligned in NE–SW and WNW–ESE directions. These en-echelon faults accommodate both dextral and vertical motions, thereby generating block rotations along their horizontal axis. As the basin margins retreat, the basin widens continuously by mass-wasting of the slopes of the inner basin. The mass-wasting, triggered by active tectonics, occurs by intense landsliding and channel erosion. The eroded material is transported into the deep basin, where it is deposited in a series of deep-sea fans and slumps. The high sedimentation rate is reflected in an over 1,500-m-thick basin fill which has accumulated in Pliocene–Quaternary times.     

Wave Data Assimilation to Modify Wind Forcing Using an Ensemble Kalman Filter

In order to improve the predictability of winter storm waves in the East Sea, this article explores the use of the ensemble Kalman filter technique for dat     

Evidence that earthquakes have been triggered by reservoir in the Song Tranh 2 region,Vietnam

In the Song Tranh 2 (ST2) hydropower reservoir located in the Quang Nam province, Central Vietnam, earthquakes started occurring soon after impoundment of the reservoir in late 2010. Earthquakes continue to occur in the region, and two earthquakes of M 4.6 and 4.7 on October 22, 2012 and November 15, 2012, respectively, have been reported (Trieu et al. 2014; Giang et al. 2015) in the vicinity of the reservoir. In the present study, b-value has been estimated, and focal mechanism solutions have been computed for the first time using moment tensor inversion approach. Also, the influence of impoundment of reservoir on the occurrence of earthquakes has been computed for the ST2 region based on Coulomb stress. A quality data set of 595 earthquakes recorded for the period of October 2012 to April 2014 at ten stations of the seismic network operated by the Institute of Geophysics (IGP) has been used to calculate b-values for the northern and southern seismicity clusters of the region. In general, the b-values associated with reservoir-triggered seismicity (RTS) are found to be higher than the regional b-values in the frequency-magnitude relation of earthquakes. For the ST2 region, it is found that the b-values for the northern and southern clusters are 0.94 ± 0.04 and 0.90 ± 0.04, respectively. Focal mechanism solutions obtained for the two earthquakes close to the reservoir have a right-lateral strike-slip mechanism, with the preferred planes trending NW-SE. These results are concurrent with the orientation of the nearby local surface faults, which we confirm as the active faults in this region. Influence of the stresses due to reservoir water load on the local seismicity is computed based on the obtained focal mechanism by using the concept of fault stability. It is found that most of the earthquakes occur in the positive Coulomb stress region, which shows the influence of reservoir impoundment on earthquake occurrence in the vicinity. Our results suggest that the local earthquakes are triggered by the impoundment of the ST2 reservoir.