Presence Of Bright Spot Research Articles

Shallow Gas Prospect Evaluation in Shahbazpur Structure Using Seismic Attributes Analysis - a Case Study for Bhola Island, Southern Bangladesh

Shahbazpur structure is located in the southern Part of the central deep basin in the Hatia trough, where lie all the largest Gas fields of Bangladesh. A method is established to delineate the structural mapping precisely by interpreting four 2D seismic lines that are acquired over Shahbazpur structure. Moreover direct hydrocarbon indicators (DHI) related attributes are analyzed for further confirmation for presence of hydrocarbon. To do this synthetic seismogram generation, seismic to well tie, velocity modelling and depth conversion are performed. A limited number of seismic attributes functions that are available in an academic version of Petrel software are applied to analyze attributes. Seismic attribute analyses that are used in this interpretation mainly are associated to bright spot detection. Presence of bright spots or high amplitude anomaly over the present Shahbazpur structure, reservoir zone are observed. This signature will play a very important role in next well planning on the same structure to test the shallow accumulation of hydrocarbon. For better understanding of this shallow reserve, it is suggested to acquire 3D seismic data over Shahbazpur structure which will help to evaluate the hydrocarbon accumulation and to identify gas migration pathways.
 Dhaka Univ. J. Sci. 64(2): 135-140, 2016 (July)

Intensity Capping: a simple method to improve cross-correlation PIV results

A common source of error in particle image velocimetry (PIV) is the presence of bright spots within the images. These bright spots are characterized by grayscale intensities much greater than the mean intensity of the image and are typically generated by intense scattering from seed particles. The displace- ment of bright spots can dominate the cross-correlation calculation within an interrogation window, and may thereby bias the resulting velocity vector. An efficient and easy-to-implement image-enhancement procedure is described to improve PIV results when bright spots are present. The procedure, called Intensity Capping, imposes a user-specified upper limit to the grayscale intensity of the images. The displacement calculation then better represents the displacement of all particles in an interrogation window and the bias due to bright spots is reduced. Four PIV codes and a large set of experimental and simulated images were used to evaluate the performance of Intensity Capping. The results indicate that Intensity Capping can significantly increase the number of valid vectors from experimen- tal image pairs and reduce displacement error in the analysis of simulated images. A comparison with other PIV image-enhancement techniques shows that Inten- sity Capping offers competitive performance, low computational cost, ease of implementation, and min- imal modification to the images.

Distortion of Normal Pituitary Structures in Sellar Pathologies on MRI

This study was undertaken to assess the displacement patterns and shifts of the normal pituitary gland in sellar pathologies on MRI and to determine if the position of the bright spot (BS) represents a predicting factor for the position of the residual adenohypophysis (RAH) in pathological conditions. In a control group of 102 patients without any pituitary pathology, the presence of the BS was evaluated. In 100 patients with intra- or suprasellar pathologies, presence and respective topography of BS and RAH were scrutinized on MRI, according to lesion type, size, endocrine status and intra-operative findings in the surgical group. The BS was visible in 91.2% of 102 cases in the control group, as compared to 75 of the 100 patients with sellar lesions. Location of RAH was identified in 58% of the patients, and RAH enhanced more than the lesion in all cases after contrast infusion. The RAH was identified in 65.3% of the 75 "BS positive" patients, as compared to 36% of the 25 "BS negative". The normal residual gland was visualized intra-operatively in 63.5% of the 52 operated patients: in 37 "BS positive" patients, it was visualized intra-operatively in 81.1% and in 28 "RAH positive" patients, it was identified in 82.1%. The BS can be identified in the majority and RAH in more than half of the cases with pituitary lesions on MRI. Positions of both the BS and RAH help predict the location of the normal residual gland during surgery and, therefore, may contribute to preserving the pituitary function.

A Led Based on Porous Polycrystalline Silicon

AbstractPrevious studies on electroluminescence in porous silicon were based on crystalline wafers. In this paper, we shall report the characteristics of a LED based on porous effects in a cast polycrystalline silicon substrate. A layer of porous region was first formed on a cast polycrystalline silicon substrate by anodization, followed by the deposition of a semitransparent Au layer. Under forward bias, the LED emits stable yellowish white light (with the presence of bright spots) for currents above 20 mA/cm2. From the electroluminescence spectra measured, we suggest that the emission is due to the recombination of electron-hole pairs in a microplasma region. We propose a model where the microplasma is present in the depletion region of the heterojunction formed between the bulk polysilicon and the surface porous polysilicon. The defects and grain boundaries in a polycrystalline material facilitate the formation of such microplasma. The heterojunction model will also be used to explain the current characteristics of the LED. The effect on the LED characteristics due to indium coating on the porous substrate prior to Au deposition was studied, and the results agree with the heterojunction model. Our work shows that cast polycrystalline silicon substrates have potential for LED fabrication in cheap and large area applications.