INTRODUCTION The purpose of this study was to compare the influences of different implant modalities on orthodontic microimplants and surrounding tissues biomechanically and histologically. METHODS Fifty-six titanium alloy microimplants placed on the buccal side of the maxillae and the mandibles in 2 dogs were divided into 2 groups of 28; one group of microimplants was self-drilling, and the ...

Most oil and gas leases allow the operator to extend possession for an indefinite period by establishing production in paying quantities. We show how this option to “hold by production” (HBP) stimulates the drilling of many wells that would otherwise be uneconomic. Although such wells may superficially appear to be poor investments, in fact they contribute to shareholder value. We also show, ho...

We have devised a method, based on a parametric array concept, to create a low-frequency (300-500 kHz) collimated ultrasound beam in fluids highly attenuating to sound. This collimated beam serves as the basis for designing an ultrasound visualization system that can be used in the oil exploration industry for down-hole imaging in drilling fluids. We present the results of two different approac...

We present a simplified drift-flux model (DFM) describing a multiphase (gas-liquid) flow during drilling. The DFM uses a specific slip law, without flow-regime predictions, which allows for transition between single and two phase flows. With this model, we design an Unscented Kalman Filter (UKF) for estimation of unmeasured states, production parameters and slip parameters using real time measu...

We study options on short-term leases for capital-intensive equipment performing specific functions and services, such as leases for semi-submersible drilling rigs, marine seismic services, corporate real estate leasing, retail space leasing, and apartment leasing. We quantify the effect of an important factor in pricing options on these services: idle time between consecutive lease contracts. ...

The Measurement/Logging While Drilling (M/LWD) system is a kind of sensors system which is used to help oil/gas drilling field technicians to steer well drilling. In M/LWD, several kinds of sensors are installed into drill string to measure the underground logging data during well drilling operations, and a sink within the drill string collects the logging data from the sensors and then transmi...

Over the past ten years, unconventional gas and oil drilling (UGOD) has markedly expanded in the United States. Despite substantial increases in well drilling, the health consequences of UGOD toxicant exposure remain unclear. This study examines an association between wells and healthcare use by zip code from 2007 to 2011 in Pennsylvania. Inpatient discharge databases from the Pennsylvania Heal...

Currently about 170 impact craters are known on Earth; about one third of those structures are not exposed on the surface and can only be studied by geophysics or drilling. The impact origin of geological structures can only be confirmed by petrographic and geochemical studies; thus, it is of crucial importance to obtain samples of subsurface structures. In addition, structures that have surfac...

1. Abstract There are several optical applications in which a mirror or lens requires accurate manipulation, for example in microscanning or focusing optical systems. Typically, such devices are designed on a trial-and-error basis. To improve on this procedure, we apply topology optimization in the design of a piezoelectric micropositioner. The mechanism employs two piezoelectric stack actuator...

The purpose of this study was to compare the performance of chemomechanical caries removal (CMCR) with that of conventional drilling for efficacy of caries removal, time spent, morphological changes and microhardness of surface dentin, and microleakage of subsequent restorations. Forty-six carious deciduous molars were randomly divided into two groups: one each for caries removal by (1) CMCR an...