An advection-robust Hybrid High-Order method for the Oseen problem

In this work, we study advection-robust Hybrid High-Order discretizations of the Oseen equations. For a given integer $k\ge 0$, the discrete velocity unknowns are vector-valued polynomials of total degree $\le k$ on mesh elements and faces, while the pressure unknowns are discontinuous polynomials of total degree $\le k$ on the mesh. From the discrete unknowns, three relevant quantities are reconstructed inside each element: a velocity of total degree $\le(k+1)$, a discrete advective derivative, and a discrete divergence. These reconstructions are used to formulate the discretizations of the viscous, advective, and velocity-pressure coupling terms, respectively. Well-posedness is ensured through appropriate high-order stabilization terms. We prove energy error estimates that are advection-robust for the velocity, and show that each mesh element $T$ of diameter $h_T$ contributes to the discretization error with an $\mathcal{O}(h_T^{k+1})$-term in the diffusion-dominated regime, an $\mathcal{O}(h_T^{k+\frac12})$-term in the advection-dominated regime, and scales with intermediate powers of $h_T$ in between. Numerical results complete the exposition

Effect of Silica Nanoparticles on the Curing Kinetics of Epoxy Vinyl Ester Resin

A nanocomposite was synthesized using silica nanoparticles (SN) and Epoxy Vinyl Ester Resin (VE671). Nanoparticles were dispersed in the mixture by ultrasonic equipment to prevent the agglomera-tion. Transmission electron microscopy (TEM) was used to investigate the dispersion of the silica nanopar-ticles in the mixture. Non-isothermal differential scanning calorimetry (DSC) technique was used to study the cure kinetics of VE671 resin with and without adding silica nanoparticles. The activation energy (Ea) was determined by using Kissinger and Ozawa equations. The Ea values of curing for VE671 / 4% SN sys-tem showed a decrease with respect to the neat resin. It means that there is a catalytic effect of silica na-noparticles in the cure reaction. A dynamic kinetic model was obtained to predict the degree of cure and cure rate of resin. The results showed a good agreement between the model and the experimental data for different heating rates. The char yields increased with the addition of 4% of SN to the epoxy resin and im-proved the polymer flame retardancy and thermal resistance at high temperatures. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3545

Preparation of PMMA/CNT Microcellular Foam Using Supercritical CO2

Controlling the cell size and cell density of microcellular foams has an important influence on polymer-ic foams properties. By using nanoparticles in polymers and supercritical fluids as foaming agent, it is pos-sible to create microcellular foams with controlled morphology. In this article surface modified carbon nanotube (CNT) was used to prepare Polymethylmethacrylate (PMMA) nanocomposite. Dry ice was used as the source of supercritical CO2 in foam production. Microcellular foams were prepared form PMMA/CNT nanocomposites. The cell morphology was observed by scanning electron microscopy (SEM) and the cell size and cell density were calculated via image analysis. The effect of CNT on cell size and cell density of foams was investigated. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3543

Modeling of Vapor Liquid Equilibrium Data for Thyme Essential Oil Based on UNIQUAC Thermodynamic Model

Vapor Liquid Equilibrium (VLE) data for natural ingredients and essential oils has not studied at all yet. It is because of the complexity of these mixtures. In this study, the equilibrium concentration of the mixture components was studied by using UNIQUAC model at different pressures. This model is capable of determining the temperature between 70°C to 170°C and the pressure limits 30 Kpa to 202 Kpa. The Modeling results showed Thymol in the liquid phase was increased from 50% molar to 90% molar in constant pressure by increasing the temperature from bubble point to dew point temperature. Thymol concentration in the liquid phase was increased from 42% molar to 78% molar by increasing the water concentration of the mixture at a constant pressure of 100 Kpa and constant temperature 177°C. Another obtaining result showed that Thymol concentration in the triple mixture, which includes 30% molar water, 35% molar Thymol, and 35% molar Cymene in liquid phase, was increased from 60% molar to 82% molar at constant temperature of 177°C by decreasing the pressure from 100 Kpa to 20 Kpa.   KEYWORDS: Essential oil, VLE, UNIQUAC, Modelin

The Distillation of Thymus Vulgaris Essence to Demonstrate TBP Curve

Based on a research project on Shirazi Thymus of the Eksir Gol Sorkh company, the essence of this Thymus included five main components, which based on the results gained from GC device, there are 5 main components in this Thymus namely ?-Pinene, ?-Terpinene, P-Cymen, ?-Terpinen, and Thymol, each of which has a percentage as follows 1.118, 3.831, 25.815, 14.771, and 54.465. With increasing the amount of Distillation, more Thymol can be achieved, and in this experiment, the amount of Thymol increases 18 percent to 92 percent. With passing of 81min from the 170 degrees Celsius, the temperature of essence solution, which is a stable 250 degrees Celsius in Heating (Oil/sand) bath, reaches 240 degrees Celsius. With an increase in the volume of Distillation material, the output water of condenser reaches up to 22.7 degrees Celsius from 21.9 degrees Celsius in such a way that incoming cold-water temperature has increased up to 21.9 degrees Celsius from 21.4 degrees Celsius by passing of time. In TBP diagram, with an increase in Distillation volume from 2 percent to 72 percent, the boiling temperature of Thymus essence solution has reached 240 degrees Celsius from 160 degrees Celsius. KEYWORDS: Distillation; Thymus; TBP; G

The Simulation of the TBP Curve of Thymol Essence and the Separation of Natural Components with ASPEN plus Software

Based on the analysis of GCMASS device, the components of the type of Thymol essence prepared from Nishabour maintains, consist of five main components namely, ?-Pinene, ?-Terpinene, P-Cymene, ?-Terpinene, and Thymol, each of which has the percentage of 1.118, 3.831, 25.815, 14.771, and 54.465 respectively in the essence. Moreover, based on the experiment, the boiling point curve for this essence was achieved, and according to the results of the analysis of the boiling point curve, the simulation for this complex mixture for achieving the characteristics of the essence was done. The simulation of the separation unit of the main components in the pressure range of 44KPa to 101.3KPa showed that with the increase of the pressure, Thymol mole fraction increases from 0.9399 to 0.9496 in the product of the bottom of the distillation column. With the increase of the total pressure of the distillation column from 44KPa to 101.3KPa, the minimum of the return reflux decreases from 17.7 to 13.93. Keywords: Simulation; TBP; Thymol Essence; Separation; ASPEN plu

Prehypertension; patient awareness and associated cardiovascular risk factors in an urban population in Iran

Background: This study was to estimate the frequency of prehypertension and to characterize patient awareness and associated cardiovascular risk factors in an urban population in Iran. Methods: During a hypertensive awareness program, a cross-sectional study was conducted on 2036 people. All participants completed a questionnaire about their demographic and anthropometric indices and were asked about symptoms, risk factors and preventive measures of hypertension. Data were compared between prehypertensive and non-hypertensive groups. Results: Prehypertension was detected in 30 (n=611) of the subjects. Previous CHD, diabetes, and hyperlipidemia were more prevalent in low prehypertension group compared to high normal blood pressure. The male sex, increasing age and body weight were positively associated with the rate of prehypertension. Only 8 of participants with prehypertension were aware about the symptoms of hypertension, 12 correctly mentioned at least three risk factors of hypertension, and 48 explained appropriate preventive measures. Conclusion: Prehypertension was prevalent in this population. Age, body weight, male sex, and previous CHD were the major determinants. Furthermore, hypertension awareness was alarmingly poor. Therefore, hypertension prevention programs focused on increasing public awareness are essential