PURPOSE To investigate the usefulness of transcranial Doppler ultrasonography in the evaluation of intracranial pressure changes after head injury. METHODS Transcranial Doppler examinations and intracranial pressure measurements using intraparenchymal monitors were performed in 12 cases of closed head injury. Twenty-four sets of data, including the Glasgow Coma Scale, intracranial pressure, t...

Fly ash resistivity is a single parameter which has got significant impact over sizing and performance of Electrostatic Precipitator (ESP) in coal based thermal power plants. A fly ash resistivity measurement facility has been set up at IIT Delhi with the support of National Energy Technology Laboratory (NETL), USA and USAID-India. The fly ash samples from different power plant are being collec...

The ability of a block inversion scheme, in which polygons are employed to define layers andror bodies of equal resistivity, in determining the geometry and true resistivity of subsurface structures has been investigated and a simple strategy for deriving the starting model is proposed. A comparison has also been made between block inversion and smooth inversion, the latter being a cell-based s...

Piezoresistivity (change of the volume electrical resistivity with strain) in continuous carbon fiber polymer-matrix structural composites allows electrical-resistance-based strain/ stress sensing. Uniaxial through-thickness compression is encountered in fastening. As shown for a 24-lamina quasi-isotropic epoxy-matrix composite, compression results in (i) strain-induced reversible decreases in ...

A stochastic Bayesian approach for combining well logs and geophysical surveys for enhancing subsurface characterization is presented. The main challenge we face is in creating the bridge to link between ambiguously related geophysical surveys and well data. The second challenge is imposed by the disparity between the scale of the geophysical survey and the scale of the well logs. Our approach ...

Using electromechanical technique, various conductive carbon fibers and graphite and steel filaments/epoxy micro-composites were evaluated by measuring electrical resistivity to investigate the interfacial properties including the microfailure modes and interfiber distance effect with a aid of acoustic emission (AE). Micromechanical techniques, such as pull-out and fragmentation tests, and elec...

A magnetotelluric monitoring station has been installed in the Val d’Agri area (southern Italy), to investigate the physics underlying the generation mechanisms of the electrokinetic effect, due to rapid pore pressure changes and fluid flows near the focal area of incoming earthquakes. It is well known that the magnetotelluric method reveals variations in electrical resistivity within the Earth...

The optimal design of production in fractured geothermal reservoirs requires knowledge of the resource’s connectivity, therefore making fracture characterization highly important. This study aims to develop methodologies to use resistivity measurements to infer fracture properties in geothermal fields. The resistivity distribution in the field can be estimated by measuring potential differences...

An automatic inverse method has been developed for generating layered earth models from electrical sounding data. The models have the minimum number of layers required to fit a resistivity sounding curve or a combined resistivity and induced polarization sounding. The ground is modeled using a very large number of thin layers to accommodate arbitrary variations. The properties of the layers are...

Carbon fiber reinforced cement is a smart material due to its sensing ability, which is based on piezoresistivity. A finite element model for simulating the measurement of electrical resistance in this material is provided. The measured four-probe resistance decreases with increasing distance between the adjacent voltage and current contacts. For a beam of size 320 × 40 × 40 mm3, the minimum di...