Flat Formations Research Articles

Numerical and Analytical Analysis of the Low-Frequency Magnetic Fields Generated by Three-Phase Underground Power Cables with Solid Bonding

There is a special concern for measuring and simulating low-frequency magnetic fields generated by underground power cables, particularly in human exposure studies. In the present study, an accurate 2D finite element model for computing magnetic fields generated by three-phase underground power cables with solid bonding is proposed. The model is developed in ANSYS Maxwell 2D low-frequency electromagnetic field simulation software for a typical 12/20 kV (medium-voltage) three-phase underground power cable in both trefoil and flat formations, but it can be adapted to any cable system. Model validation is achieved by analytical computations conducted with a software tool based on the Biot–Savart law and the superposition principle. RMS magnetic flux density profiles calculated at various heights above the ground with these two methods correlate very well. This is also true for induced shield currents. The application of the finite element model to multiple three-phase power cables laid together is also considered.

Method of localization of agricultural robotic vehicles using AESA established by an UAV complex

This paper considers a relevant method to ensure communication and object location in vast agricultural areas. To solve this problem an operational scenario was proposed, an approach, involving a complex of several UAVs, which establish an AESA; an algorithm for building an optimal path, along which the UAV complex moves, formulas for calculating AESA direction pattern for linear and flat formations of UAV groups, formulas for calculating time, required for terrain scanning with various areas. In such complex on each UAV an antenna with phase shifter is mounted. The paper also considers modeling and comparison of different approaches to motion of an UAV complex for terrain scanning. Due to application of active electronically scanned arrays, the proposed localization method is characterized by high noise immunity, is better shielded from noise, less dependent on weather conditions and appliable at night time. Unlike other methods, it supports wide-range transmission and reception of data. Thereby, application of AESA makes this method robust and practical for localization and communication establishment, whereas the proposed algorithm for building of optimal path, along which the robotic complex moves, enables to reduce time, required for area scanning. Consequently, this method allows achieving the shortest distance that the UAV complex has to cover.

Quasi-3D Perfect Absorber Based on the Self-Similar Parasitic Elements as an Optical Sensor with Tunable Attributes for Near-Infrared Application

We have designed a novel self-similar plasmonic perfect absorber with a quasi-three-dimensional (3D) shape based on parasitic elements, which is useful as a refractive index sensor for near-infrared applications. In order to achieve tunable attributes, we have applied the liquid crystal medium to provide a tunable structure which can be considered to control the absorption parameter and resonances. In fact, we have proposed a self-similar structure to obtain a multi-band structure in the range of 800–1600 nm with an absorption value up to 99.8%. The basic model is a single cross element, while each quarter is filled up by L-shaped elements by forming a tapered shape like a pyramidal in which the elements are arranged from large to small with various heights and lengths which creates a ziggurat form. So this structure can provide a quad-band absorber which we have implemented as a refractive index sensor with a much higher figure of merit (FOM) in comparison to the flat formations. For the final structure, the maximum values of the FOM and sensitivity (S) are 24,560 RIU−1 and 660 nm RIU−1, respectively.

Spin stiffness of bilayer zigzag graphene nanoribbon for several configurations

Abstract The spin stiffness of the bilayer zigzag graphene nanoribbon for several configurations was obtained by means of the total energy difference of the flat spiral formations within the self-consistent calculation. To realize it, the penalty functional was employed to fix the direction of the magnetic moment of the carbon atom at the edges. Using the experimental lattice constant and the interlayer distance, the results showed that the total energy of each configuration is inversely proportional to the spin stiffness, which implies that the most stable configuration has the highest spin stiffness. For the final discussion, we also justified that the most stable configuration is not robust to the interlayer distance.

Arrangement Optimization of Power Cables in Harmonic Currents to Achieve the Maximum Ampacity Using ICA

In this article, a new electro-thermal optimization algorithm is proposed to determine the parallel power cables arrangement to obtain the maximum ampacity. The optimization procedure is based on the imperialist competitive algorithm (ICA). Electrical calculations are performed using the sub-conductors method and consideration of the skin and proximity effects. FEM thermal model and electrical calculations are coupled with optimization procedure to determine the ampacity in the optimization algorithm. Optimized arrangements are determined under sinusoidal and harmonic load currents conditions. Furthermore, the effects of different boundary conditions of the ground surface such as isothermal and convective heat flux are evaluated. The underground single conductor cables with solid bonded metallic sheaths and existing of circulating currents are considered. Cables are considered to be installed adjacent to each other in different rows above each other in flat formations. Also, the artificial bee colony (ABC) optimization algorithm is performed to validate the ICA procedure. Experimental measurement of a case study is carried out for simulation confirmation and the results show good agreement.

Calculation of losses and ampacity derating in medium-voltage cables under harmonic load currents using finite element method

Summary This paper investigates the influence of metallic sheaths on alternating current (AC) losses and ampacity of power cables. The AC losses are expressed as AC/direct current (DC) resistance in power cables, which is the main factor in loss computations. With regard to the importance of harmonic contents of the currents, a comprehensive study is performed on AC/DC resistance of medium-voltage cables in the presence of harmonics. Different harmonic frequencies include triple and nontriple orders are considered. A derating factor is proposed on the basis of cable constructions. Two types of sheathed and unsheathed medium-voltage power cables are considered. Also for metallic sheathed cables, 2 types of sheath grounding are investigated. It is shown that single-point bonding and both-ends bonding of sheaths have different effects on cable ampacity in harmonic frequencies. Moreover, different conductor cross sections and distances between cables are considered, and their effects on AC/DC resistance and ampacity derating are assessed. It is shown that these factors have important effects on AC/DC resistance and thus power cable losses. Furthermore, all cases are investigated in both flat and trefoil formations that are the most popular formations in power cables. To achieve precise results, we performed this study on the basis of finite element simulation, which is an exact way to cable losses computations in each configuration.

Geology and geochronology of the Emu Creek Block (northern New South Wales, Australia) and implications for oroclinal bending in the New England Orogen

The southern part of the New England Orogen exhibits a series of remarkable orogenic bends (oroclines), which include the prominent Z-shaped Texas and Coffs Harbour oroclines. The oroclines are defined by the curvature of Devonian–Carboniferous forearc basin and accretionary complex rock units. However, for much of the interpreted length of the Texas Orocline, the forearc basin is mostly concealed by younger strata, and crops out only in the Emu Creek Block in the eastern limb of the orocline. The geology of the Emu Creek Block has hitherto been relatively poorly constrained and is addressed here by presenting new data, including a revised geological map, stratigraphic sections and new detrital zircon U–Pb ages. Rocks of the Emu Creek Block include shallow-marine and deltaic sedimentary successions, corresponding to the Emu Creek and Paddys Flat formations, respectively. New detrital zircon U–Pb data indicate that these formations were deposited during the late Carboniferous and that strata were derived from a magmatic source of Devonian to Carboniferous age. The sedimentary provenance and detrital zircon age distribution suggest that the sequence was deposited in a forearc basin setting. We propose that the Emu Creek and Paddys Flat formations are arc-distal, along-strike correlatives of the northern Tamworth Belt, which is part of the forearc basin in the western limb of the Texas Orocline. These results confirm the suggestion that Devonian–Carboniferous forearc basin rocks surround the Texas Orocline and have been subjected to oroclinal bending.

Parametric Study of Losses in Cross-Bonded Cables: Conductors Transposed Versus Conductors Nontransposed

Conductor transposition, for cross-bonded cables, is recommended in the ANSI/IEEE Standard 575-1988 as a means to reduce interference with communication systems. In this paper, it is shown that reduced interference comes at the price of increased cable losses, which is an issue not addressed in the 1998 edition of the IEEE Standard 575. Analytical formulas are obtained for the calculation of the positive-sequence resistance for transposed and not transposed conductors to shed light on the reasons why the losses increase when the conductors are transposed. It has been found that for cross-bonded cables installed in flat formations, the positive-sequence resistance of transposed conductors is always larger than that of nontransposed conductors. Parametric studies are performed by varying all of the construction and installation parameters that affect the value of the positive-sequence resistance. In particular, we have changed the separation distance between cables, the insulation thickness, the number and resistance of the concentric wires, and the resistivity of the soil among other parameters. Examples on transmission and distribution cables are discussed.

Use of Pressure/Rate Deconvolution To Estimate Connected Reservoir-Drainage Volume in Naturally Fractured Unconventional-Gas Reservoirs From Canadian Rockies Foothills

Summary Case studies are presented in this paper to demonstrate the use of the pressure/rate deconvolution-approach in estimating drainage areas for wells completed in some of the naturally fractured tight gas reservoirs of the Canadian Rockies foothills. These case studies demonstrate the application of deconvolution to two key carbonate-stratigraphical horizons in the area: the Triassic Baldonnel and the Permo-Carboniferous Taylor Flat formations. In these structural plays with significant areal formation-rock heterogeneity, the matrix-rock properties controlling the gas storativity are low, with porosity between 3 and 6%, causing low matrix-rock permeability (from 0.01 and 0.1 md). However, all of these formations have been thrusted, overturned, and subjected to reverse faulting. These diagenetic factors have created swarms of natural fractures that control flow rates and may define rock volumes connected to individual wells. In each well, a preproduction flow test was performed with the intent of ensuring acceptable flow rates and scoping facility design. At this stage of early development, initial-gas-in-place (IGIP) estimates were derived mainly from geophysical mapping, with plans to calibrate the IGIP number through the application of gas material balance, rate-transient analysis, and/or simple late-time rate decline. The rate-history data available in the early stage of production were integrated with pressure-buildup (PBU) data collected later in the production life of the well during annual or routine shut-in periods that were relatively short. Application of deconvolution in this paper is aimed at detecting early signs of pseudosteady-state pool depletion and estimating connected drainage volume. The deconvolution procedures help calibrate and/or reconcile geosciences-defined volumetric resource sizes, map remaining reserves, and help identify possible infill-drilling opportunities.

Estimation of stormwater flow through railway ballast

Seepage flow through railway ballast is estimated, with the aim of reducing design flows in conventional stormwater drainage components. Flow-head equations are derived for ballast on flat and superelevated railway formations. A simple but effective experimental determination of frictional parameters of the ballast material is described, with guidelines on selecting appropriate model scale and range of test conditions. Some test results are discussed, and a method of allowing for different ballast size and porosity is proposed. Justification is given for allowing for ballast flow in drainage design, discussing circumstances in which the additional flow capacity was and was not allowed.

Volcanisme triasique calco-alcalin a shoshonitique du Nevada occidental

Volcanisme triasique calco-alcalin a shoshonitique du Nevada occidental

Structural style and tectonic evolution of a polyphase extensional basin of the Gulf of Lion passive margin: the Tertiary Alès basin, southern France

The Alès basin is one of the Tertiary onshore basins of the Gulf of Lion margin, related to Oligo-Aquitanian rifting of the NW Mediterranean. This basin is presently exposed in the landwardmost part of the margin, along the Cévennes Fault, a major structural feature that was active during Variscan (Carboniferous) orogeny, Tethyan (Lias) rifting, and Pyrenean (early–middle Tertiary) compression. Combined field studies and seismic reflection profiles analyses show that the geometries of the Tertiary extensional fault systems and related hangingwall, and the architecture of syn-rift sediments are genetically related. This analysis makes it possible to re-evaluate the structural style and the kinematics of the Tertiary Alès sedimentary basin. Our results indicate two distinct architectures for the late Eocene and Oligocene syn-rift deposits, respectively, that were controlled by two different extensional systems: • During late Eocene, the basin was a half-graben formed along a simple listric fault responsible for the development of a hangingwall roll-over, and north-west divergence of syn-rift infill. The bordering extensional fault (the Alès Fault) is a listric fault passing at depth to a SE-dipping low-angle ramp corresponding to the Triassic marl and evaporite beds. This fault is distinct from the inherited high-angle Cévennes Fault that affects the Palaeozoic basement. • During Oligocene, a complex ramp-flat extensional system reactivated the deep part of the late Eocene extensional system and was responsible for the formation of a hangingwall syncline basin. The latter displays progressive unconformities within synrift continental sediments onlaping the hangingwall flat. Alluvial-fan clasts are exclusively derived from the hangingwall flat formations and were deposited along a NE-trending syncline parallel to the basin border. During extension, depocentres migrated north-westward, as a result of ongoing extension and of erosion of the hangingwall flat. Extension on the Alès Fault propagated upwards and north-westwards across the Mesozoic formations, while the low-strength marl beds of the Neocomian formed flats, and the emerging ramp was superimposed on to the Cévennes Fault at surface level. The late Eocene ramp was then passively transported down-dip. The Oligocene tectono-sedimentary system suggests (1) an original extensional system where inherited high-angle faults were not reactivated, but localized the emergence of a decollement propagating within the Trias formations, and (2) the presence of Mesozoic (up to Neocomian) cover on the Cévennes margin during Oligocene; consequently, the Palaeozoic basement presently exposed in the footwall was exhumed later. The rift basins that developed along the Cevennes fault do not fit with the landward boundary of stretched continental crust, which is located tens of kilometres to the SE, the Nimes Fault. Although they are often well exposed for field studies, rift basins in the hinterland of continental margins are not always representative of the tectonics of the whole margin, and should therefore be integrated with caution in studies of continental passive margins.