High Transverse Resistance Research Articles

Inward eccentric fold failure in the progressive crushing of aluminum-CFRP square hybrid tubes

To explore the enhancement mechanism of CFRP overwrap in the aluminum-CFRP square hybrid, hybrid tubes with different braided angles were investigated both experimentally and numerically. Hybrid tube of 30 degrees had severe CFRP layers splitting damage in the tube corner. As the braided angle up to 60 degrees, CFRP layers with high transverse resistance force compressed the aluminum tube and caused it to fold inward; This led to the hybrid tube failing in a distinct inward eccentric fold deformation pattern and had an obvious energy absorption improvement in its inner aluminum tube due to its increase in the corner deformation.

Estimation of Dar-Zarrouk parameters and delineation of groundwater potential zones in Karlahi, part of Adamawa Massif, Northeastern Nigeria

Karlahi is largely underlain by granites and migmatites gneiss of the Adamawa Massif. The area lies west of Benue Trough and east of Cameroon volcanic line. The aim of this paper is to determine hydraulic properties of water bearing layer using parameters derived from Dar-Zarrouk equation and characterized them into groundwater potential zones. The resistivity values of the weathered and slightly weathered layers which make up the water bearing layers were added and an average was taken and used as the resistivity of the water bearing formation in computation of Dar-Zarrouk parameters in Karlahi area. The values of resistivity of water bearing formation ranged from 18 to 4963 Ωm with an average resistivity value of 549 Ωm and the thickness of the water bearing formation ranges from 21 to 32 m with an average thickness of 24.5 m. Conductivity values range from 0.000201 to 0.05509 (σ) while the longitudinal conductance range from 0.00483 to 1.2363 Ω-1, the transverse resistance ranges from 407 to 123504.3 Ωm2. The hydraulic conductivity and transmissivity values range from 0.14 to 25.87 m/day and 3.28 to 580.4 m2/day respectively. The longitudinal conductance values in Karlahi area revealed poor to good with an average longitudinal conductance value that is moderate. High transverse resistance values are located in the central and southern part of Karlahi area while low values are located in the eastern part. The spatial distribution map of transmissivity in the area revealed moderate to high transmissivity values in the north central part and a negligible to low transmissivity in southern part, extreme northeastern part. The groundwater potential map of Karlahi area shows negligible to weak potential groundwater zones in SW and SE, moderate potential in the central to northern part of Karlahi area.

Magnetization AC Losses of Quasi-Isotropic Strand Stacked by 2G Wires at 77 K

This paper numerically and experimentally investigates the magnetization ac losses in quasi-isotropic strand under external ac magnetic field at 77 K. The measurements of ac losses were carried out by the pick-up coil method in ac magnetic field at amplitudes from 0.03 to 0. 25 T and at frequencies between 20 and 100 Hz. Simulations made by a two-dimensional finite element method (FEM) model based on H -formulation were performed to predict the measured results. Because of the short length of sample and the existence of high transverse resistance between interwires in strand, the measured ac losses agree well with the simulation of magnetically uncoupled case. The coupling length of quasi-isotropic strand is found to be 1.422 m, based on the measured equivalent transverse resistivity of 1.342 mΩ·m. The full penetrated field of the strand at 77 K is 0.132 T, across which the frequency dependence of magnetization ac losses in strand becomes completely inversed. The systematic study on magnetization ac losses of quasi-isotropic strand could be the base for their applications in high field magnets.

Delineation of Groundwater Potential and Recharge Zone Using Electrical Resistivity Method Around Veeranam Tank, Tamil Nadu, India

Veeranam tank is one of the largest tank in Tamil Nadu, India which plays a vital role in groundwater recharge to the surrounding aquifer. Electrical resistivity survey were carried out in ten locations around the Veeranam tank. The resistivity, thickness of subsurface formations, longitudinal conductance (S), transverse resistance (R), average longitudinal resistivity (ST), average transverse resistivity (RT) and anisotropy (λ) were used to characterize the lithological formations and also groundwater potential and recharge zones were delineated. The four major zones clay, clayey sand, saline sand and sandstone were identified as a result of primary geo-electrical parameters which includes resistivity and thickness of the formations. The sandstone formation is identified as good water bearing formation and this formation possess low longitudinal conductance, high transverse resistance, and low anisotropy values. The clay and saline formation possess high longitudinal conductance, low transverse resistance and high anisotropy values and these formations are identified as moderate groundwater water bearing formations. High longitudinal conductance is observed in eastern region of the study area due to intrusion of saline water. Sandstone formation of low longitudinal conductance is associated with high percolation rate and groundwater potential is also good in this formation. High transverse resistance zones are associated with high infiltration rate and high transmissivity whereas groundwater potential is good in these zones. VES 2 and VES 3 stations comprises of sandstone formation as second layer and Veeranam tank water infiltrated into these zones due to high infiltration rate of these formations. The resistivity value is decreased in VES 10 station due to intrusion of sea water. The true resistivity near the Veeranam tank is high and decreases towards east which clearly indicates that groundwater recharge is the major process that occurs nearby the downstream shore of tank and intrusion of saline water in the eastern part of the study area. Thus good interaction between exists between Veeranam tank and its downstream zones and interaction decreases as the distance increases from the tank.

波状曲げ変形を受けたNb<sub>3</sub>Sn 素線の臨界電流特性評価手法の開発

A cable-in-conduit (CIC) conductor using Nb3Sn strand is applied to an ITER TF coil. The Nb3Sn strand in the conductor is periodically bent due to electromagnetic force, which causes degradation of performance. This degradation should be evaluated to predict conductor critical current performance. In a past study, a numerical simulation model was developed to evaluate the superconductivity of a periodically bent single strand. However, this model is not suitable for application to strands in the conductor because of the extensive calculation time required. The author thus developed a new analytical model with a much shorter calculation time to evaluate the performance of periodically bent strand. This new model uses the classical model concept of a high transverse resistance model (HTRM). The calculated results show good agreement with the test results of a periodically bent Nb3Sn strand in a ends fixed beam model while there was little error in the uniformly bent model under high transverse load due to the difference in bending moment distribution between the two models. However, for both cases, the newly developed model has a much shorter calculation time than that required for numerical simulation. This indicates that a more practical solution can be achieved when evaluating the performance of periodically bent strands. Thus, the model developed in this study can be applied to evaluation of the performance of conductor incorporating many strands.

Using Geoelectric Soundings for Estimation of Hydraulic Characteristics of Aquifers in the Coastal Area of Lagos, Southwestern Nigeria

Electrical resistivity investigation was carried out at Ibeju Lekki, Southwestern Nigeria. The thrust of this study is to determine the geoelectrical parameters of the shallow aquifer and estimate the hydraulic characteristics of this aquifer unit from the surface geophysics. The area falls within the Dahomey basin of the Nigeria sedimentary terrain. Twenty-one VES were conducted using Shlumberger array with a maximum half current electrode (AB/2) of 100 m giving total spread of 200 m. Data were interpreted using partial curve matching technique and assisted 1-D forward modeling with WINRESIST software. The qualitative interpretation revealed KQ curves (ρ1 < ρ2 > ρ3 > ρ4) and KH curve (ρ1 < ρ2 > ρ3 < ρ4). The geoelectric section generated from the results of the VES revealed a four geo-electric layers; these include topsoil with resistivity ranging from 213-5404 Ωm, dry sand with resistivity values vary from 301to 17178 Ωm, saturated sand with resistivity varying from 110 to1724 Ωm and sand (saline water content) with resistivity values of between 8 and 97 Ωm. The major aquifer in the area occurs at the third geoelectric layer. The depth to this aquifer is of between 0.7m and 6.0m and the layer thickness is between 0.2 m and 19.9 m. The hydraulic characteristics of the aquifer estimated from the geoelectric parameters reveal that the aquifer has porosity values of between 29.4 % and 57.7 %, protective capacities of between 0.00013 and 0.015 mhos, transverse resistance ranges from 345-18502 Ωm2, transmissivity values vary from 13 to 310 m2/day and hydraulic conductivity ranges from 0.8-65 m/day. The results show that the aquifer is characterized by high porosity and low protective capacities of overburden layers indicating that it is highly vulnerable to surface contamination. It has high transverse resistance, high transmissivity, and high hydraulic conductivity indicating that the aquifer can transmit water at higher rate and sustain the need of the community. This study has demonstrated the efficacy of surface geophysics in estimating hydraulic characteristics of an aquifer where pumping test data are not available and also to determine its vulnerability to surface contaminants.

Using Geoelectric Soundings for Estimation of Hydraulic Characteristics of Aquifers in the Coastal Area of Lagos, Southwestern Nigeria

Electrical resistivity investigation was carried out at Ibeju Lekki, Southwestern Nigeria. The thrust of this study is to determine the geoelectrical parameters of the shallow aquifer and estimate the hydraulic characteristics of this aquifer unit from the surface geophysics. The area falls within the Dahomey basin of the Nigeria sedimentary terrain. Twenty-one VES were conducted using Shlumberger array with a maximum half current electrode (AB/2) of 100 m giving total spread of 200 m. Data were interpreted using partial curve matching technique and assisted 1-D forward modeling with WINRESIST software. The qualitative interpretation revealed KQ curves (ρ1 < ρ2 > ρ3 > ρ4) and KH curve (ρ1 < ρ2 > ρ3 < ρ4). The geoelectric section generated from the results of the VES revealed a four geo-electric layers; these include topsoil with resistivity ranging from 213-5404 Ωm, dry sand with resistivity values vary from 301to 17178 Ωm, saturated sand with resistivity varying from 110 to1724 Ωm and sand (saline water content) with resistivity values of between 8 and 97 Ωm. The major aquifer in the area occurs at the third geoelectric layer. The depth to this aquifer is of between 0.7m and 6.0m and the layer thickness is between 0.2 m and 19.9 m. The hydraulic characteristics of the aquifer estimated from the geoelectric parameters reveal that the aquifer has porosity values of between 29.4 % and 57.7 %, protective capacities of between 0.00013 and 0.015 mhos, transverse resistance ranges from 345-18502 Ωm2, transmissivity values vary from 13 to 310 m2/day and hydraulic conductivity ranges from 0.8-65 m/day. The results show that the aquifer is characterized by high porosity and low protective capacities of overburden layers indicating that it is highly vulnerable to surface contamination. It has high transverse resistance, high transmissivity, and high hydraulic conductivity indicating that the aquifer can transmit water at higher rate and sustain the need of the community. This study has demonstrated the efficacy of surface geophysics in estimating hydraulic characteristics of an aquifer where pumping test data are not available and also to determine its vulnerability to surface contaminants.

Determination of Aquifer Properties and Groundwater Vulnerability Mapping Using Geoelectric Method in Yenagoa City and Its Environs in Bayelsa State, South South Nigeria

Nineteen Schlumberger vertical electrical soundings (VES) were carried out within and around Yenagoa city, South South Nigeria, using a maximum current electrode separation ranging between 300 - 400 m. The objectives of the study were 1) to evaluate the possibility of mapping Quaternary sediments to infer the geological structure from the electrical interpretation and identify formations that may hold fresh water with low concentration of conducting minerals such as iron 2) to evaluate the vulnerability of the aquifer in the study area. The interpretation of the data collected was by computer assisted iterative interpretation using 1-D inversion technique software (1X1D, Interpex, USA). The results of the interpretation revealed four distinct geoelectric layers. Sounding curve types obtained in the area are mostly of the form ρ1 > ρ2 ρ3 ρ4 (where ρ is the density) but fresh water lenses with low concentration of conducting minerals such as iron were obtained only in locations that exhibit ρ1 > ρ2 ρ3 ρ4 curve types. Depth to the aquifer ranges from 4.5 m in the vicinity of VES 05 to 27.0 m at the vicinity of VES 14. The resistivity of the aquiferous horizon varies between 60 - 2868 Ωm. High transverse resistance values obtained were associated with zones of high transmissivity which agrees with the geology of the Benin Formation (Coastal Plain sands) consisting of fine-medium-coarse sands. The aquifer vulnerability map illustrates the impermeability of the overburden clay layer. Values of >0.5 mhos indicate good protective capacity, while values <0.3 mhos indicate vulnerable zones with probable risk of contamination.

Analytical model of the critical current of a bentNb3Sn strand

The critical current performance of a largeNb3Sn cable-in-conduit conductor (CICC) was degraded by periodic bending of strands due to alarge transverse electromagnetic force. The degradation of each strand due to this bendingshould be evaluated in calculations of the critical current of a CICC, but a suitable modelhas not been developed yet. Therefore, the authors have developed a new analytical modelwhich takes into account plastic deformation of copper and bronze and filamentbreakage. The calculated results were compared with test results for uniformly bentNb3Sn bronze-route strands. The calculated results assuming a high transverse resistance model(HTRM) show good agreement with the test results, a finding which confirms the validity of themodel. Because of a much shorter calculation time than for numerical simulation, the developedmodel seems much more practical for use in calculating the critical current performance of aNb3Sn CICC. In addition, simulation results show that since the neutral axis of a bent strandshifts to the compressive side due to plastic deformation of the copper and bronze, and/orfilament breakage, the strand is elongated by bending. This elongation may enhance thestrand’s critical current performance. Moreover, the calculated results indicate thatthe dependence of the critical current on the bending strain is affected by thebending history if the strand is excessively bent, especially when filaments arebroken. In a real magnet, since a strand in a CICC is normally subject to themaximum electromagnetic force prior to an evaluation of its performance at a lowerelectromagnetic force, the effect of over-bending should be taken into account incalculations of its critical current performance, especially when filament breakage occurs.

DC Performance of Subsize NbTi Cable-in-Conduit Conductors

Five subsize NbTi cable-in-conduit conductors with parametric variations were fabricated and their DC performance was tested in the SULTAN facility. A comparison of the measured strand data and the cable performances clearly indicates that the current carrying capacity of the conductors is considerably reduced due to the self-field effect. This result reflects that because of the high transverse resistance the interstrand current sharing is not very efficient. Furthermore, the take-off electric field was found to decrease monotonously with increasing quench currents. In the case of large overall current densities, sudden take-offs occur before the critical current criterion (0.1 /spl mu/V/cm) has been reached. The observed quench behavior is a consequence of the large contribution of the self-field to the total magnetic field, which leads to strongly enhanced electric fields in the strands on the high field side of the conductor. As soon as the heat generated in the peak field region exceeds the locally available cooling power a quench is initiated. Considering insulated strands and a uniform current distribution the quench behavior has been reproduced by simulations.

Computer simulations of three-dimensional propagation in ventricular myocardium. Effects of intramural fiber rotation and inhomogeneous conductivity on epicardial activation.

Three-dimensional membrane-based simulations of action potential propagation in ventricular myocardium were performed. Specifically, the effects of the intramural rotation of the fiber axes and inhomogeneous conductivity on the timing and pattern of epicardial activation were examined. Models were built, with approximately 400,000 microscopic elements arranged in rectangular parallelepipeds in each model. Simulations used the nonlinear Ebihara and Johnson membrane equations for the fast sodium current. Constructed models had histological features of ventricular myocardium. All models were anisotropic. In a subset of the models, an abrupt intramural rotation of the fiber axes was included. This feature was also combined with randomly distributed inhomogeneous conductivity and regions of high transverse resistance to represent nonuniform anisotropy in a further subset of the models. Epicardial stimuli were applied for each simulation. Three-dimensional activation patterns and epicardial isochron maps were constructed from the simulations. We noted that the rotation of fiber axes accelerated epicardial activation distant from the stimulus site. The inhomogeneous conductivity caused regional acceleration and deceleration of activation spread. We also noted features of epicardial activation that resulted from the fiber rotation, and the inhomogeneous conductivity corresponded to that observed in maps from experimental animals.