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A new nanoporous carbon from tomato paste waste (TWNC) was prepared. The surface area, total pore volume, average pore diameter of TWNC was found as 722.17 m2 g-1, 0.476 cm3 g-1 and 2.644 nm, respectively. The effects of solution pH, adsorbent dose, initial concentration, ionic strength, contact time, and temperature were studied. Adsorption kinetics was found to be best represented by the pseudo second order model. Isotherm data were fitted well to the both Langmuir and Freundlich models. Maximum adsorption capacity was found as 68.97 mg g-1 at 50 ℃. Thermodynamic parameters showed that the process was spontaneous and endothermic.
In this work, an elastic-plastic stress analysis has been conducted for silicon carbide fiber reinforced magnesium metal matrix composite beam. The composite beam has a rectangular cross section. The beam is cantilevered and is loaded by a single force at its free end. In solution, the composite beam is assumed perfectly plastic to simplify the investigation. An analytical solution is presented for the elastic-plastic regions. In order to verify the analytic solution results were compared with the finite element method. An rectangular element with nine nodes has been choosen. Composite plate is meshed into 48 elements and 228 nodes with simply supported and in-plane loading condations. Predictions of the stress distributions of the beam using finite elements were overall in good agreement with analytic values. Stress distributions of the composite beam are calculated with respect to its fiber orientation. Orientation angles of the fiber are chosen as 0° , 30°, 45°, 60° and 90°. The plastic zone expands more at the upper side of the composite beam than at the lower side for 30°, 45° and 60° orientation angles. Residual stress components of σX and τxy are also found in the section of the composite beam.<br/>
Feedbacks signals of rotor speed and motor torque are essential in most of Switched Reluctance (SR) motor control applications. An SR motor has highly nonlinear characteristics that do not allow to be modeled by simple equations. Hence, the feedback signals can not be mathematically calculated from the model. Instead of calculation, they should be measured or estimated. In Direct Torque Control (DTC) drive, which enables easy control of torque ripple in the SR motor, position sensor is employed to obtain the feedback signals. Position sensor causes DTC drive not only less reliable but also more expensive. Estimation of feedback signals is required in order to eliminate position sensor (or encoder). This paper concerns about sensorless speed estimation under the DTC condition and presents a simple method. The proposed method is based on inductance vector angle. The inductance vector angle is obtained by applying α ? β transformation to the phase inductances. A relay triggers a speed calculation circuit according to its band limits and the inductance vector angle. Inside the circuit, triggering time is kept in a memory until the next triggering. Then, rotor pole pitch is divided by the time difference between two consecutive triggerings. Finally, the estimation circuit outputs the rotor speed. Estimation method is simulated and verified experimentally to show its validity.
In this paper, the properties of the cement mortar modified with styrene acrylic ester copolymer were investigated. Expanded vermiculite as lightweight aggregate was used for making the polymer modified mortar test specimens. To study the effect of polymer–cement ratio and vermiculite-cement ratio on various properties, specimens were prepared by varying the polymer–cement and vermiculite-cement ratios. Tests of physical properties such as density, water absorption, thermal conductivity, three-point flexure and compressive tests were made on the specimens. Furthermore, a coupled thermal-structural finite element model of an entire corner wall was modelled in order to study the best material configuration. The wall is composed by a total of 132 bricks of 120 × 242 × 54 size, joined by means of a contact-bonded model. The use of advanced numerical methods allows us to obtain the optimum material properties. Finally, comparisons of polymer–cement and vermiculite-cement ratios on physical properties are given and the most important conclusions are exposed.
This study aims to monitor the variation of modal frequencies of steel buildings during their construction sequence. In this respect, construction of a steel building is followed by vibration based measurements. The monitored building is a three-story educational building within a building group whose structural system consists of steel moment resisting steel frames and eccentric braces. Five different acceleration measurements in two perpendicular directions are taken on five different construction stages, starting from the erection of the columns and beams ending with the completion of the construction. The recorded measurements are transferred into frequency domain and the dominant frequencies for each case have been determined. The change in the dominant frequencies is evaluated with the existing construction stages and performed constructional works between the stages. The last measurement, performed on the building in service, revealed the first two dominant frequencies as mutual in X and Y direction, showing that these dynamic modes are torsional modes. This result is investigated by numerical analysis performed with finite element model of the building constructed for design purpose. Lower frequencies and different mode shapes are determined from numerical analysis. The reason of lower frequencies is discussed and the vibration survey is extended to determine the effects of an adjacent building. The results showed that the building is in strong relation with an adjoining building in spite of a designed construction joint.
This study analyzes especially drag and lift models recently developed for fluid-solid, fluid-fluid or liquidliquid two-phase flows to understand their applicability on the computational fluid dynamics, CFD modeling of pulsatile blood flow. Virtual mass effect and the effect of red blood cells, RBCs aggregation on CFD modeling of blood flow are also shortly reviewed to recognize future tendencies in this field. Recent studies on two-phase flows are found as very useful to develop more powerful drag-lift models that reflect the effects of blood cell's shape,deformation, concentration, and aggregation.
The purpose of this study is mainly directed towards present of viewpoints on critical and commentary analysis on blood rheology, blood viscosity models, and physiological flow conditions. Understanding these basics is fundamental to meet the need for a sufficient and reliable CFD model of blood. Most of the used viscosity models on this manner have determined from parameter fitting on experimental viscosity data. Availability of experimental data from literature to define viscosity models of CFD analysis should be accurately chosen and treated in order to avoid any errors. Several basic gaps that limit the CFD model results are identified and given opportunities for future research. The purpose of this study is mainly directed towards present of viewpoints on critical and commentary analysis on blood rheology, blood viscosity models, and physiological flow conditions. Understanding these basics is fundamental to meet the need for a sufficient and reliable CFD model of blood. Most of the used viscosity models on this manner have determined from parameter fitting on experimental viscosity data. Availability of experimental data from literature to define viscosity models of CFD analysis should be accurately chosen and treated in order to avoid any errors. Several basic gaps that limit the CFD model results are identified and given opportunities for future research.
The influence of the presence of neighboring entities on drag in blood flow where the dominating mechanisms are expected to be viscous, drag, and gravity forces is investigated in a 3-D anatomically realistic right coronary artery. A classical Eulerian multiphase model on the Fluent v6.3.26 platform is used to model pulsatile non-Newtonian blood flow. Two new drag models based on the mixture viscosity concept are developed by using the drag similarity criteria. In literature, drag models based on the mixture viscosity concept are only depended on volume fraction and show Newtonian viscosity effects on drag. However, mixture viscosity depends on the primary independent variables such as the volume fraction and the shear rate in most of the dispersed flows like blood flow. Non-Newtonian drag effects on red blood cell are so calculated by using these new volume fraction and the shear rate dependent drag models. Five different drag models including these new drag models are used to model the blood flow in this study to investigate the effectiveness of drag force model on blood flow.