An efficient algorithm for overlapping bubbles segmentation

Image processing is an effective method for characterizing various two-phase gas/liquid flow systems. However, bubbly flows at a high void fraction impose significant challenges such as diverse bubble shapes and sizes, large overlapping bubble clusters occurrence, as well as out-of-focus bubbles. This study describes an efficient multi-level image processing algorithm for highly overlapping bubbles recognition. The proposed approach performs mainly in three steps: overlapping bubbles classification, contour segmentation and arcs grouping for bubble reconstruction. In the first step, we classify bubbles in the image into a solitary bubble and overlapping bubbles. The purpose of the second step is overlapping bubbles segmentation. This step is performed in two subsequent steps: at first, we classify bubble clusters into touching and communicating bubbles. Then, the boundaries of communicating bubbles are split into segments based on concave point extraction. The last step in our algorithm addresses segments grouping to merge all contour segments that belong to the same bubble and circle/ellipse fitting to reconstruct the missing part of each bubble. An application of the proposed technique to computer generated and high-speed real air bubble images is used to assess our algorithm. The developed method provides an accurate and computationally effective way for overlapping bubbles segmentation. The accuracy rate of well segmented bubbles we achieved is greater than 90 % in all cases. Moreover, a computation time equal to 12 seconds for a typical image (1 Mpx, 150 overlapping bubbles) is reached

GPU acceleration of edge detection algorithm based on local variance and integral image: application to air bubbles boundaries extraction

Accurate detection of air bubbles boundaries is of crucial importance in determining the performance and in the study of various gas/liquid two-phase flow systems. The main goal of this Accurate detection of air bubbles boundaries is of crucial importance in determining the performance and in the study of various gas/liquid two-phase flow systems. The main goal of this Accurate detection of air bubbles boundaries is of crucial importance in determining the performance and in the study of various gas/liquid two-phase flow systems. The main goal of this work is edge extraction of air bubbles rising in two-phase flow in real-time. To accomplish this, a fast algorithm based on local variance is improved and accelerated on the GPU to detect bubble contour. The proposed method is robust against changes of intensity contrast of edges and capable of giving high detection responses on low contrast edges. This algorithm is performed in two steps: in the first step, the local variance of each pixel is computed based on integral image, and then the resulting contours are thinned to generate the final edge map. We have implemented our algorithm on an NVIDIA GTX 780 GPU. The parallel implementation of our algorithm gives a speedup factor equal to 17x for high resolution images (1024×1024 pixels) compared to the serial implementation. Also, quantitative and qualitative assessments of our algorithm versus the most common edge detection algorithms from the literature were performed. A remarkable performance in terms of results accuracy and computation time is achieved with our algorithm. work is edge extraction of air bubbles rising in two-phase flow in real-time. To accomplish this, a fast algorithm based on local variance is improved and accelerated on the GPU to detect bubble contour. The proposed method is robust against changes of intensity contrast of edges and capable of giving high detection responses on low contrast edges. This algorithm is performed in two steps: in the first step, the local variance of each pixel is computed based on integral image, and then the resulting contours are thinned to generate the final edge map. We have implemented our algorithm on an NVIDIA GTX 780 GPU. The parallel implementation of our algorithm gives a speedup factor equal to 17x for high resolution images (1024×1024 pixels) compared to the serial implementation. Also, quantitative and qualitative assessments of our algorithm versus the most common edge detection algorithms from the literature were performed. A remarkable performance in terms of results accuracy and computation time is achieved with our algorithm. work is edge extraction of air bubbles rising in two-phase flow in real-time. To accomplish this, a fast algorithm based on local variance is improved and accelerated on the GPU to detect bubble contour. The proposed method is robust against changes of intensity contrast of edges and capable of giving high detection responses on low contrast edges. This algorithm is performed in two steps: in the first step, the local variance of each pixel is computed based on integral image, and then the resulting contours are thinned to generate the final edge map. We have implemented our algorithm on an NVIDIA GTX 780 GPU. The parallel implementation of our algorithm gives a speedup factor equal to 17x for high resolution images (1024×1024 pixels) compared to the serial implementation. Also, quantitative and qualitative assessments of our algorithm versus the most common edge detection algorithms from the literature were performed. A remarkable performance in terms of results accuracy and computation time is achieved with our algorithm

Dynamique spatio-temporelle d'un jet d'air libre évoluant à nombre de Reynolds modéré

Ce travail présente des résultats expérimentaux pour un jet d'air libre injecté dans l'air ambiant à nombre de Reynolds 1600. La dynamique du jet est observée par visualisation des images de l'écoulement des fumées d'encens enregistrées par une caméra rapide. Une analyse temporelle des séries d'images acquises a permis de mettre en évidence les détails du comportement de l'écoulement. Les résultats démontrent l'existence d'anneaux tourbillonnaires au bord du jet. La taille, la distribution et la fréquence d'apparition de ces anneaux tourbillonnaires sont examinées

Primary resistance to clarithromycin, metronidazole and amoxicillin of Helicobacter pylori isolated from Tunisian patients with peptic ulcers and gastritis: a prospective multicentre study

<p>Abstract</p> <p>Background</p> <p>The frequency of primary resistance to antibiotics in H. pylori isolates is increasing worldwide. In Tunisia, there are limited data regarding the pattern of H. pylori antibiotic primary resistance.</p> <p>Aim</p> <p>To evaluate the primary resistance of H. pylori to clarithromycin, metronidazole and amoxicillin and to detect the mutations involved in clarithromycin resistance.</p> <p>Materials and methods</p> <p>273 strains isolated from adults and children were enrolled. The primary resistance to clarithromycin, metronidazole and amoxicillin was evaluated by means of E-test minimal inhibitory concentration (MIC). The real-time PCR using Scorpion primers was performed in all cases to assess clarithromycin primary resistance and point mutations involved.</p> <p>Results</p> <p>No resistance to amoxicillin was detected. For adults, resistance to clarithromycin and metronidazole was found respectively in 14.6% and 56.8%, and respectively in 18.8% and 25% in children. Overall, the rates of global primary resistance to clarithromycin and metronidazole in Tunisia were respectively determined in 15.4% and 51.3%.</p> <p>By the use of Scorpion PCR, the A2143G was the most frequent point mutation observed (88.1%), followed by the A2142G (11.9%); the A2142C was not found and 18 of 42 patients (42.8%) were infected by both the resistant and the susceptible genotype.</p> <p>The association of clarithromycin resistance with gender was not statistically significant, but metronidazole resistant strains were isolated more frequently in females (67.8%) than in males (32.2%) and the difference was significant. As for gastroduodenal diseases, the difference between strains isolated from patients with peptic ulceration and those with non peptic ulceration was not statistically significant. When about the distribution of resistant strains to clarithromycin and metronidazole between the three Tunisian cities (Tunis, Menzel Bourguiba and Mahdia), the difference was not statistically significant.</p> <p>Conclusion</p> <p>Local data regarding the primary resistance of H. pylori to clarithromycin, metronidazole and amoxicillin and the main genetic mutation involved in clarithromycin resistance in vivo (A2143G) are necessary to prove a clear need for a periodic evaluation of antibiotic consumption and new therapeutic strategies in Tunisia in order to avoid the emergence of resistant strains.</p

Imaging study of various instabilities on the jet structure : application to the jet control

L’isolation par rideaux d’air, avant d’être un confort, est actuellement un enjeu énergétique majeur. Malgré toutes les évolutions dans ce domaine, la nature du régime de l’écoulement du rideau d’air reste un facteur très influant sur les performances et la qualité de l’isolation. Il est impératif de trouver comment le stabiliser et éviter ou éloigner la région de la turbulence. Dans ce contexte, on a mis en oeuvre un ensemble d’outils de traitements d’images spécifiques aux textures présentes dans les images du jet rond basé sur des techniques de rehaussement d’images issues des méthodes d’interpolation. Plusieurs analyses de séquences d’images avec suivi spatio-temporel ont été effectuées en vue de prédire le passage à la turbulence. Une modélisation géométrique originale a été développée pour une meilleure compréhension du mouvement 3D du jet rondBefore being a comfort, the air curtain insulation is currently a major energy issue. Despite all the developments in this field, the nature of the air curtain flow regime remains a very influential factor on the performance and quality of insulation. It is imperative to find ways to stabilize it and to prevent the turbulence zone. In this context, we have implemented a set of specific processing tools for image textures present in the round jet images. Several analysis of image sequences with spatio-temporal monitoring were performed to predict the transition to turbulence. Original geometric modeling has been developed for better understanding of the 3D motion of the round je

Spectral analysis of round jet instabilities at low Reynolds number

For the study of round jet flow at low Reynolds number, a fine analysis of instabilities is necessary. In this paper, we present a frequency analysis of temporal and spatial velocity variations in a round jet with a Reynolds number equal to 830. The data were obtained from Laser Doppler Anemometry (LDA) measurements for various downstream positions. Attention is focused on the characteristics of the instantaneous signal of the longitudinal velocity component u(t) in order to characterize the transition from laminar state to turbulent state. The spectral analysis of the LDA signals of the axial component of the exit velocities highlights the presence of a single peak of energy around a characteristic frequency f0. This frequency corresponds to the amplified mode of the instability. The jet develops a sinuous mode which is the most unstable anti-symmetric mode. The results obtained in this study concerning the sinuous mode frequency, agree well with those obtained by laser tomography technique and images analysis

Association of Fas/Apo1 gene promoter (-670 A/G) polymorphism in Tunisian patients with IBD

AIM: To detect a possible association between the polymorphism of the (-670 A/G) Fas/Apo1 gene promoter and susceptibility to Crohn’s disease (CD) and ulcerative colitis (UC) in the Tunisian population. METHODS: The (-670 A/G) Fas polymorphism was analyzed in 105 patients with CD, 59 patients with UC, and 100 controls using the polymerase chain reaction restriction fragment length polymorphism method. RESULTS: Significantly lower frequencies of the Fas -670 A allele and A/A homozygous individuals were observed in CD and UC patients when compared with controls. Analysis of (-670 A/G) Fas polymorphism with respect to sex in CD and UC showed a significant difference in A/A genotypes between female patients and controls (P corrected = 0.004 in CD patients and P corrected = 0.02 in UC patients, respectively). Analysis also showed a statistically significant association between genotype AA of the (-670 A/G) polymorphism and the ileum localization of the lesions (P corrected = 0.048) and between genotype GG and the colon localization (P corrected = 0.009). The analysis of inflammatory bowel disease patients according to clinical behavior revealed no difference. CONCLUSION: Fas-670 polymorphism was associated with the development of CD and UC in the Tunisian population