A coupled FEM/BEM approach and its accuracy for solving crack problems in fracture mechanics

AbstractThe finite element (FEM) and the boundary element methods (BEM) are well known powerful numerical techniques for solving a wide range of problems in applied science and engineering. Each method has its own advantages and disadvantages, so that it is desirable to develop a combined finite element/boundary element method approach, which makes use of their advantages and reduces their disadvantages. Several coupling techniques are proposed in the literature, but until now the incompatibility of the basic variables remains a problem to be solved. To overcome this problem, a special super-element using boundary elements based on the usual finite element technique of total potential energy minimization has been developed in this paper. The application of the most commonly used approaches in finite element method namely quarter-point elements and J-integrals techniques were examined using the proposed coupling FEM–BEM. The accuracy and efficiency of the proposed approach have been assessed for the evaluation of stress intensity factors (SIF). It was found that the FEM–BEM coupling technique gives more accurate values of the stress intensity factors with fewer degrees of freedom

Robust H∞ Control of Takagi–Sugeno Systems with Actuator Saturation

Producción CientíficaThe robust static output feedback control for continuous-time Takagi–Sugeno systems subject to actuator saturation is solved here, including H∞ performance guarantees. Based on a polytopic model of the saturation, sufficient conditions are proposed for designing these controllers in terms of Linear Matrix Inequalities. With the aid of some special derivations, bilinear matrix inequalities are converted into a set of linear matrix inequalities which can be solved easily without requiring iterative algorithms or equality constraints, moreover, the output matrix of the considered system does not require to be full row rank. Finally, some examples are presented to show the validity of the proposed methodology

Une tumeur du vagin à ne pas méconnaitre, l’adénocarcinome mésonephrique: à propos d’un cas et revue de la literature

L'adénocarcinome mésonéphrique du vagin est une tumeur maligne extrêmement rare avec uniquement trois cas publiés dans la littérature jusqu'à maintenant. Il dérive des reliquats embryonnaires des canaux mésonéphriques au niveau du vagin. Nous rapportons un cas d'adénocarcinome mésonéphrique du vagin survenant chez une femme de 50 ans, et révélé par une masse polyploïde du vagin. L'IRM a montré un envahissement du périnée et de la branche inférieure du pubis. L'étude anatomo-pathologique était en faveur d'un adénocarcinome mésonéphrique dont les cellules tumorales expriment la pancytokératine et le CD10. Elles ne sont pas marquées par les anticorps anti récepteurs ostrogéniques et progestatifs. La patiente a été adressée pour radiothérapie avant la prise en charge chirurgicale. Les auteurs soulignent à travers cette observation les aspects étiopathogéniques, histologiques et thérapeutiques de cette tumeur rare

Assessment of Dapagliflozin Effectiveness as Add-on Therapy for the Treatment of Type 2 Diabetes Mellitus in a Qatari Population

The effectiveness of dapagliflozin in the management of type-2 diabetes mellitus (T2-DM) is an essential issue for establishing a basis for prescribing dapagliflozin. This study aimed to assess the effectiveness of dapagliflozin in combination with other hypoglycemic agents (OHAs) in reducing glycated hemoglobin (HbA1c) and fasting blood glucose (FBG) at 3, 6, 9 and 12 months. This retrospective observational study included all patients who visited the endocrine clinics at Hamad Medical Corporation (HMC) and were treated with dapagliflozin. Demographics and laboratory data were obtained retrospectively from computerized patient medical profiles (eMR-viewer). The main outcome measures were the differences in HbA1c and FBG from baseline at different months. Eighty-one Qatari patients were found to have received dapagliflozin during the study period; 72% of them (n = 58) were males, with a mean age of 57.0 ± 9.0 years and a mean baseline HbA1c of 9.0 ± 1.4%. Administration of dapagliflozin as an add-on therapy was found to decrease HbA1c significantly by 0.8 percentage point after 6 months (P = 0.006) and by 1.5 percentage point after 12 months (P = 0.062). FBG was significantly reduced at 6 months and 9 months (P = 0.001 and P = 0.03, respectively). Dapagliflozin effectively reduced the HbA1c level and FBG when used in combination with other OHAs or insulin within 6 to 12 months. © 2019, The Author(s).Ethical approval. This study was approved by the Institutional Review Board at the Medical Research Center of Hamad Medical Corporation. The authors would like to thank the Hamad Medical Corporation for proving the research funding. This work was supported by the Medical Research Center of Hamad Medical Corporation [grant number 15292/15].Scopu

Ovarian Cancer in the Sudan - Identifying the Social and Clinical Factors that Prevent an Early Diagnosis

Ovarian cancer, because it often presents with vague symptoms, is a difficult disease to diagnose at the early stages, especially in developing countries. In Sudan, diagnosis is further complicated by additional factors and challenges. First, as in any developing country, access to treatment, facilities and medical staff is generally lacking. Secondly, Sudan is the second largest country in Africa: its very size presents difficulties for the implementation of a centralized health system. The two tertiary hospitals in or near the capital have long patient waiting lists.The lack of female education in sub-Saharan Africa, together with social and economic issues affecting women, is a further obstacle to disease diagnosis and management. Misdiagnosis, leading to inappropriate treatment, may result from the presence of comorbid diseases such as Tuberculosis (TB), which can mimic ovarian cancer and obstruct early detection. Most patients are identified at the later stages when the complications associated with invasive procedures and conventional chemotherapy make treatment much less effective. The early detection of biomarkers may prove to be a vital tool to indicate targets for immunotherapy treatment.Financial aid may help improve the outcomes for patients with ovarian cancer in the Sudan, assisting with diagnosing and management procedures including training medical staff. Research and development, documentation and updating the statistical register for the whole country are also important requirements for future improvements.Finally, there is a need to promote interdisciplinary work between surgeons and clinical oncologists to optimize international guidelines and protocols in accordance with the facilities available

Study of State Estimation Using Weighted Least Squares Method

Power state estimation constitutes the core of the on-line security analysis function. The challenge number one of a state estimator is to provide the optimal estimates of system state with minimum of measurement data. This paper describes weighted least squares state estimation method and investigates how the efficiency of WLS state estimation changes according to 4 parameters: number of measurements, measurement type, measurement weight and level of noise. Different simulation cases are tested on 3-bus system and IEEE 14-bus system. The results show that accurate estimates of system state can be obtained with minimum of measurement data on condition to choose a good combination of accurate measurements with a minimum of voltage measurements and power injection measurements and these data should be properly distributed throughout the system. For best results, the two factors (weight and noise) must be combined to obtain the best estimation. Indeed, the most accurate measurements (lower level of noise) should have greater weight compared to bad measurements (higher level of noise), specially voltage measurements due to their big impact

CO2 and H2 Adsorption and Reaction at Nin/YSZ(111) Interfaces: A Density Functional Theory Study

To recycle CO2 into sustainable fuels and chemicals, coelectrolysis of CO2 and H2O can be achieved in solid oxide electrolysis cells, where the molecules are supplied to the Ni/YSZ electrode (YSZ = yttria-stabilized zirconia). Oxygen diffusion along the electrode has been identified as the critical step in the process, where YSZ is the common catalyst support. We have investigated the interaction of a CO2 molecule with the clean YSZ(111) surface and with Nin/YSZ(111) (n = 1, 4–7, 10, and 20) interfaces, using a spin-polarized density functional theory and a long-range dispersion correction. Here, we have considered up to six initial adsorption sites and two orientations for the CO2 molecule, which showed that the adsorption is stronger at the Nin/YSZ(111) (n = 4–7, 10, and 20) interface than on the clean YSZ(111) and Ni1/YSZ(111) systems. Additionally, we have determined that the preferential adsorption site of CO2 is at the interface between the Ni clusters and the YSZ(111) surface. We have observed a bending and stretching of the molecule, demonstrating its activation upon adsorption, because of charge transfer between the metal cluster and the molecule and a mixing between Ni orbitals and CO2 orbitals. In this work, we show that although the electronic structure of the clusters depends on the cluster size, the interaction strength of CO2 with the interface is independent of the size of the supported nickel particle. Finally, we have considered the reverse water gas shift reaction and determined the hydrocarboxylic intermediate in the reaction mechanism over Ni5/YSZ(111)