Numerical modeling of the thermal contact in metal forming processes

Heat flow across the interface of solid bodies in contact is an important aspect in several engineering applications. This work presents a finite element model for the analysis of thermal contact, which takes into account the effect of contact pressure and gap dimension in the heat flow across the interface between two bodies. Additionally, the frictional heat generation is also addressed, which is dictated by the contact forces predicted by the mechanical problem. The frictional contact problem and thermal problem are formulated in the frame of the finite element method. A new law is proposed to define the interfacial heat transfer coefficient (IHTC) as a function of the contact pressure and gap distance, enabling a smooth transition between two contact status (gap and contact). The staggered scheme used as coupling strategy to solve the thermomechanical problem is briefly presented. Four numerical examples are presented to validate the finite element model and highlight the importance of the proposed law on the predicted temperature.The authors gratefully acknowledge the financial support of the Portuguese Foundation for Science and Technology (FCT) under the project PTDC/EMS-TEC/1805/2012 and by FEDER funds through the program COMPETE Programa Operacional Factores de Competitividade, under the project CENTRO-07-0224- FEDER-002001 (MT4MOBI). The second author is also grateful to the FCT for the postdoctoral grant SFRH/BPD/101334/2014. The authors would like to thank Prof. A. Andrade-Campos for helpful contributions on the development of the finite element code presented in this work.info:eu-repo/semantics/publishedVersio

Computer Vision and Machine Learning for Glaucoma Detection

Deep learning based on computer vision and machine learning is an emerging technology in both the medical imaging industry and academia. Despite the existence of some commercial glaucoma detection systems such as retinal imaging, OCT scans, and ocular tonometry, we are at the beginning of a long research pathway toward the future generation of intelligent glaucoma detection systems. Early glaucoma diagnosis prevents permanent structural optic nerve damage and consequent irreversible vision impairment. Longitudinal studies have described both baselines structural and functional factors that predict the development of glaucomatous change in ocular hypertensive and glaucoma suspects. Although there is neither a gold standard for disease diagnosis nor progression, photographic assessment of the optic nerve head remains a mainstay in the diagnosis and management of glaucoma suspects and glaucoma patients. This thesis discusses several image processing techniques comprising disparity map, superpixel and noise removal for pre-processing. A stack of traditional classifiers was utilized as a hybrid model based on the ensemble method to generalise and boost the performance of the proposed model to detect glaucoma through the thickness of the retina. A method was needed aiming at both detecting pathologic changes characteristic of glaucomatous optic neuropathy in optic disc images, and classification of images into categories of glaucomatous/suspect or normal optic discs. Therefore, different machine learning algorithms were used including transfer learning, deep convolutional neural networks, and deep multilayer neural networks that extract features automatically based on clinically relevant optic disc features. Meanwhile, biomarkers were demonstrated with the proposed deep learning model to interpret which parts of the retina had been affected by glaucoma. Finally, this research proposes methods based on evolving deep pre-trained learning architecture, stereo matching with the usage of disparity maps, hybrid models with statistical analysis to retinal nerve fibre layer (RNFL) classification, and visualization of biomarkers with deep learning to detect glaucoma in early stages based on fundus images. Besides, in Appendix A; we discuss a hypothesis of glaucoma detection through detecting specified pattern with signal processing and video processing to achieve glaucoma detection at its early stages. Thus, we are going to specify the OKN pattern of eye movement to detect glaucoma at its initial stage

Different type of periodontitis and gingivitis in patients with major thalassemia comparing to healthy people

BACKGROUND AND AIM: Iran is located on the thalassemia belt and has the highest prevalence rate of patients compared to the general population in the world. This investigation was performed to determine the prevalence of gingivitis and periodontitis in thalassemia patients in comparison to healthy people and evaluate the relationship between periodontal disease and age, gender, splenectomy and dosage of desferal. METHODS: In this cross-sectional study, 133 thalassemia patients and 133 healthy people were examined. Clinical examination was performed by periodontal probe and age, gender, desferal dosage, smoking, occlusion, dental alignment were recorded. The results were analyzed using ANOVA, Chi-square, and t-test. RESULTS: Prevalence of gingivitis and periodontitis in thalassemia patients was significantly higher than the control group (P = 0.049). However, no difference was observed in the severity of periodontitis. Results showed that age, xerostomia and splenectomy are associated with periodontitis, and dental alignment was correlated with gingivitis. Calculus index (CI) was reported to be more in thalassemia patients, but results showed no significant difference in debris index (DI) however DI was significantly higher in anterior maxillary sextant. CONCLUSION: Due to the higher prevalence of gingivitis and periodontitis in patients with thalassemia and susceptibility to infection, preventive and therapeutic treatment is essential in these patients. KEYWORDS: Major Thalassemia, Gingivitis, Periodontitis, Splenectomy, Desfera

A New System for Measuring Auto-Fluorescence Changes in Neovascular-AMD after Intravitreal Injection of Bavecizumab

Age-Related Macular Degeneration (AMD) is the second disease diabetes which causes blindness in aged people. The only remedy for AMD is intravenous injection of bavecizumab. To prove the efficiency of remedy, the degenerated cells in Macula should be measured. In this article, a modern system is introduced to measure Auto-Fluorescence in Macula part of retina in order to obtain number of degenerated cells. The system consists of three main parts: Pre-processing stage is omission of margins and reversion of images in retina. Analysis stage is in charge of classification of images and elicitation of their features. In classification the target areas are identified by methods like morphology, dynamic threshold and connected comportments and the features of target area including Euclidean distance to the center of image and density. In the stage of understanding by gathering the features of each class, we will get the measurable parameter of evaluating Auto Fluorescence by the help of which we can count the number of degenerated cells of Macula area. The results are coming from statistical analysis, including linear regression and correlation of data. Experiments have been done on a database of 34 retina images of AMD patients. The average statistical error rate is equal to76 percent. In clinical reviews, the founded relation to disinflation of Macula has been proved, while there were no proved relations to the vision decreasing or increasing of patients

In Vitro Antifungal Efficacy of Different Intracanal Irrigants against Candida Albicans

Background and Aim: An intracanal irrigant is essential for a successful root canal ther-apy. The aim of this study was to compare the antifungal efficacy of 5.25% sodium hypochlorite, 2% chlorhexidine gluconate (CHX) and 94% carvacrol against Candida albicans (C. albicans) in vitro. Materials and Methods: In this experimental study, after crown removal and canal prep-aration of 48 extracted human maxillary central incisors, they were randomly divided into 3 experimental groups of 14 teeth, plus two groups of positive and negative controls (n=3). A suspension of C. albicans (ATCC=10261) was injected into the experimental and positive control group root canals. The teeth were then incubated for 72 hours. Then, root canals in each group were rinsed with one of the irrigants for 1 minute and samples were taken from the canals and inoculated on plates. After 48 hours of incubation, the colony growth was assessed and colony forming units (CFUs) served as a measure of antifungal activity. Data were analyzed using the Kruskal Wallis test. Results: In carvacrol, sodium hypochlorite and CHX groups, 6, 10 and 1 specimen did not show bacterial growth and the mean CFU was 86.3, 53.3 and 271.2 in the mentioned groups, respectively. Conclusion: Carvacrol and 5.25% sodium hypochlorite had similar antifungal efficacy against C. albicans and this effect was significantly greater than that of 2% CHX