Deep Electrical Resistivity Tomography for the Hydrogeological Setting of Muro Lucano Mounts Aquifer (Basilicata, Southern Italy)

The proposed work concerns the application of a deep geoelectrical survey to a carbonate aquifer in order to define the best location for exploitation well drilling for increasing water supply. However, an optimal characterization of a groundwater resource is the necessary condition to reach the indicated aim. Therefore, the geoelectrical investigation was guided from the previous geological and hydrogeological characterization. Moreover, geophysical methods are good tools to improve the groundwater model when detailed information is necessary, such as the localization of a pumping well. The work summarizes the hydrogeological knowledge at the West of the Basilicata Region (Muro Lucano, Italy). The investigated area is characterized by the presence of a karst aquifer which is made up of a carbonate ridge (Castelgrande, Muro Lucano) that tectonically dips southward and is widely covered by Pliocene deposits (sands and conglomerates), by the Irpinian unit and Sicilide unit formations, and by debris slope and landslide deposits. The assessment of the complex hydrogeological framework of the area was detailed by the use of a new multichannel deep geoelectrical technique (DERT). In details, the proposed technique was able to successfully locate a less resistive zone connected to a more fractured limestone and then it was suitable for the localization of a groundwater exploitation well.

Research on Microstructure and Electrical Resistivity of Injection Molded Metallic Fiber-Filled Polymer Composites

The electrical resistivity of metal fiber-filled polymer composite always increases during injection molding process because the conductive fibers were easily broken down to shorter under the action of high shear stress. In order to decrease electrical resistivity of the molding, we investigated the microstructure at different layers within the molding made from stainless steel fiber-filled polypropylene and measured their resistivities. High resistive zone mediate resistive zone and low resistive zone were found within the molding. The results showed that the high resistivity zone located at the skin area of the molding where average length of filled fibers was less than other zones, and the smallest resistive zone located at the core area where most fibers preserved large ratio of length to diameter and oriented along flowing direction of the melt, and the sub-skin zone is mediate resistive zone.

Investigation of Hierarchically Branched-Microchannel Coolers Fabricated by Deep Reactive Ion Etching for Electronics Cooling Applications

The removal of high heat fluxes from BeO ceramic and GaN-on-SiC semiconductor dies using hierarchically branched-microchannel coolers is investigated, in order to examine the impact of the number of branching levels on performance. The microchannel coolers are made by lithography and deep reactive ion etching of single crystal silicon. The test dies contain a dc-operated resistive zone that approximates the spatially averaged heat flux that would appear in low-temperature cofired ceramic microwave circuit packages and in monolithic microwave integrated circuits. For the particular geometric constraints selected for the study (three source/exhaust channels, ∼5×5 mm2 die footprint, 200 μm deep channels in a 400 μm thick silicon wafer), the optimum performance is achieved with three hierarchical levels of branched-channel size. A heat flux of 1.5 kW/cm2 is removed from the 3.6×4.7 mm2 resistive zone of the BeO-based die, at a surface temperature of 203°C. When attached instead to a high thermal conductivity GaN-on-SiC die with a 1.2×5 mm2 resistive zone, a heat flux of 3.9 kW/cm2 is removed from the resistive zone at 198°C surface temperature. The total water flow rate is 275 ml/min in both situations. The experimental results are found to be in reasonable agreement with finite element simulations based on idealized estimates of convection coefficients within the channels. For the three-channel size configuration, an effective heat transfer coefficient in the range of 12.2–13.4 W/cm2 K (with respect to a 20°C bulk fluid temperature) is inferred to be present on the top of the microchannel cooler, based on simulations and derived values obtained from the experimental data.

Resistivity mapping using inductive sources

In electromagnetic (EM) exploration for conductive targets, measurements of the magnetic component or its time derivative have received more theoretical attention and practical application than have measurements of the electric component. However, the electric component can be shown to be particularly useful in the search for resistive zones not usually detected by the magnetic component. Normalized measurements of the surface voltage differences caused by the constant current induced at late time by the UTEM transmitter are called 'Inductive Source Resistivity' or ISR measurements.Data collected on a grid located just south of the Temora gold mine in N.S.W. clearly show the effectiveness of the ISR technique in detecting a resistive zone of silicification located unconformably under 10S of conductive cover. Due to the relatively slow falloff of the electric field from an inductive source, the technique is ideal for the rapid exploration of large areas.

On the theory of sea‐floor conductivity mapping using transient electromagnetic systems

The electrical conductivity of the sea floor is usually much less than that of the seawater above it. A theoretical study of the transient step‐on responses of some common controlled‐source, electromagnetic systems to adjoining conductive half‐spaces shows that two systems, the horizontal, in‐line, electric dipole‐dipole and horizontal, coaxial, magnetic dipole‐dipole, are capable of accurately measuring the relatively low conductivity of the sea floor in the presence of seawater. For these systems, the position in time of the initial transient is indicative of the conductivity of the sea floor, while at distinctly later times, a second characteristic of the transient is a measure of the seawater conductivity. The diagnostic separation in time between the two parts of the transient response does not occur for many other systems, including several systems commonly used for exploration on land. A change in the conductivity of the sea floor produces a minor perturbation in what is essentially a seawater response. Some transient responses which could be observed with a practical, deep‐towed coaxial magnetic dipole‐dipole system located near the sea floor are those for half‐space, the layer over a conductive or resistive basement, and the half‐space with an intermediate resistive zone. The system response to two adjoining half‐spaces, representing seawater and sea floor, respectively, is derived analytically. The solution is valid for all time, provided the conductivity ratio is greater than about ten, or less than about one‐tenth. The analytic theory confirms the validity of numerical evaluations of closed‐form solutions to these layered‐earth models. A lateral conductor such as a vertical, infinite, conductive dike outcropping at the sea floor delays the arrival of the initial crustal transient response. The delay varies linearly with the conductance of the dike. This suggests that time delay could be inverted directly to give a measure of the anomalous integrated conductance of the sea floor both between and in the vicinity of the transmitter and the receiver dipoles.