Improving the accuracy of a solid spherical source radius and depth estimation using the diffusion equation in fluorescence reflectance mode

For a point or a spherical source in infinite space the steady state potential is simply a constant over the distance from the source. Flow of soil gases was studied by comparing results for other cavity shapes for sources (or sinks) to the spherical solution. Cavity shapes included a vertical line source of finite length, a prolate spheroid with a vertical axis of rotation, and a vertical well also of finite length and radius. Questions addressed include the distance over which the differences between a sphere and the alternatives become negligible and what radius of spherical source at a given pressure results in the same flow rate as from the other shapes. For a vertical line source the pressure is within 5% of the pressure for the spherical source at a distance of 2.5 times the vertical line and within 1% beyond 6 times the vertical line. Similar results were expressed for the other shapes relative to a spherical source. Travel times are presented in a generalized relationship illustrated for spherical and finite line sources. The results are relevant to other potential problems as well, for example, steady water flow in saturated porous media, steady water flow in unsaturated porous media without gravity, heat conduction, diffusion, and electrostatics.

A hybrid particle swarm–Nelder–Mead optimization method for crack detection in cantilever beams

Results are presented of an experimental study of particle ejection from the shocked free surface of metal samples of planar and cylindrical geometry. The potential of the current diagnostic methods for studying the phenomenon is discussed.

The flux and current of radiation at the surface of shielded sources are calculated as a function of source radius and shield thickness. Curves are presented for source radius (or half-thickness) from 0 to 20 mean-freepaths and for shield thickness from 0 to 20 mean-free-paths for plane, cylindrical, and slab geometries. The curves are particularly useful for estimating flux leakage from large systems. Since Pe/sup T/ rather than P is the plotted function. the curves do not sacrifice accuracy. (auth)

A model to explain forward bias capacitance-voltage measurements is presented and compared with experimental results. Forward bias capacitance-voltage measurements, with environment light, were performed in a sample containing CdSe ultra thin quantum wells periodically embedded on undoped epitaxially grown ZnSe on a semi-insulating GaAs(001) substrate. A Au Schottky contact and annealed Ti/Pt/Au ohmic contacts were deposited on the sample surface in a coplanar cylindrical geometry. Under this model both type of carriers are necessary to explain the capacitive (holes) and resistive (electrons) behaviors. The measurements are fitted following the presented model, reasonable agreement is obtained. The quality factor Q is calculated and it is found to be smaller than one, hence no correction is needed. The charge carrier density profile is done on the capacitance voltage measurement. The experiments indicate a periodic charge distribution in the samples attributed to charge captured in the ultra thin quantum wells.

Optical imaging of fluorescent probes is an essential tool for investigation of molecular events in small animals for drug developments. In order to get localization and quantification information of fluorescent labels, CEA-LETI has developed efficient approaches in classical reflectance imaging as well as in diffuse optical tomographic imaging with continuous and temporal signals. This paper presents an overview of the different approaches investigated and their performances. High quality fluorescence reflectance imaging is obtained thanks to the development of an original "multiple wavelengths" system. The uniformity of the excitation light surface area is better than 15%. Combined with the use of adapted fluorescent probes, this system enables an accurate detection of pathological tissues, such as nodules, beneath the animal's observed area. Performances for the detection of ovarian nodules on a nude mouse are shown. In order to investigate deeper inside animals and get 3D localization, diffuse optical tomography systems are being developed for both slab and cylindrical geometries. For these two geometries, our reconstruction algorithms are based on analytical expression of light diffusion. Thanks to an accurate introduction of light/matter interaction process in the algorithms, high quality reconstructions of tumors in mice have been obtained. Reconstruction of lung tumors on mice are presented. By the use of temporal diffuse optical imaging, localization and quantification performances can be improved at the price of a more sophisticated acquisition system and more elaborate information processing methods. Such a system based on a pulsed laser diode and a time correlated single photon counting system has been set up. Performances of this system for localization and quantification of fluorescent probes are presented.

Ultrasonic flaw sizing is important issue for remaining life prediction of industrial plants. Time-of-Flight Diffraction (TOFD) method is recognized as one of the most accurate flaw sizing method. However, to measure the crack height accurately, the crack must be symmetrically placed between transmitter and receiver. When the crack do not exist such position, the B-scan is required for accurate crack sizing. By the way, if additional transmitter or reciever is added to the system, the crack location and height can be estimated without B-scan. In this study, we examined the 4 sensor TOFD method which utilizes two transmitters and two receivers. In the result, the crack location and height can be estimated by 4 sensor TOFD method. However, the estimation errors were large due to the low SN ratio of received signal. Then we applied the pulse compression technique to the 4 sensor TOFD method for improving SN ratio of received signal. In the result, the SN ratio was enhanced about 11 dB by the pulse compression. The average location on error is reduced from 2.49 mm to 1.13 mm, and the average depth estimation error is reduced from 0.28 mm to 0.21 mm.

In this study, we developed a dynamic positioning sensing (DPS) system for estimating size and depth of embedded objects. The DPS System is comprised of a tactile imaging sensor (TIS), a near infrared diffuse optical imaging (DOI) unit. The TIS have a flexible and transparent sensing probe, a LED (light emitting diode) module, and a CCD camera with lens. The light from the LED-illuminated probe is scattered when a force is applied to the probe, and captured by the camera as a tactile image. TIS determined the tumor size by correlating applied force, depth and number of pixel in tactile image. On the other hand, using a near infrared laser as source and the CCD camera as detector, we obtained the diffuse optical images. From these images, we computed the absorption coefficient of the embedded tumor phantom. We maneuvered the source-detector simultaneously for collecting diffuse optics information. We termed this maneuver as dynamic positioning. The TIS provided a priori location information. The combination of the absorption coefficient, tactile data, and dynamic positioning method improved the size and depth estimation. The experimental results showed that the TIS estimated the tumor phantom size with 7.23% error, while the DPS System measured the size with 0.8% error. The TIS depth estimation error was 41.83%, and the DPS System reduced depth measurement error to 20.67%.

We introduce for the first time the novel idea of manipulating the momentum coupling coefficient using plasma confinement and shock wave reflection from the cavity walls. The plasma was confined using cylindrical geometries of various cavity aspect ratios to manipulate the momentum coupling coefficient (Cm). The Nd: YAG laser (532 nm, 5 ns pulse duration) was focused on the ferrite sample surface to produce plasma in a region surrounded by cylindrical cavity walls. The multiple reflections of the shockwaves from the cavity walls confined the laser-induced plasma to the central region of the cavity that subsequently resulted in a significant enhancement of the momentum coupling coefficient values. The plasma shielding effect has also been observed for particular values of laser fluencies and cavity aspect ratios. Compared with the direct ablation, the confined ablation provides an effective way to obtain high Cm values.