Effects of Hybridization of Carbon and Polypropylene Short Fibers as Reinforcement on Flexural Properties of Fine Aggregate Concretes

Nowadays, the advantages of short fibers as reinforcement in cement based materials are well known. In this paper, the effect of hybridization of short polypropylene (PP) and carbon fibers on flexural properties of a fine aggregate concrete has been investigated. Samples with dimensions of  containing 2 vol% of the polypropylene and carbon fibers with 6 and 8mm length were made. The PP to carbon fiber proportion in the samples were selected as 100:0, 75:25, 50:50, 25:75 and 0:100. A four-point bending test was carried out on all the samples to investigate the flexural behaviour. It was found that the addition of carbon fibers significantly increases the flexural load (i.e. 260%). The application of PP fibers leads to a 2590% increase in the toughness compared to the control sample. It was also found that the sample with carbon to PP ratio of 75/25 shows the optimum results and it leads to 190% and 2070% increment in the flexural load and toughness, respectively, in comparison to the control sample

Applying the genetic algorithm for determination electrospinning parameters of poly vinylidene fluoride (PVDF) nano fibers: theoretical & experimental analysis

Poly Vinylidene Fluoride (PVDF) because of its piezoelectric properties has been applied in different applications such as smart textiles, medical application and membranes for energy harvesting. It was declared that nanofibres diameters and electrospinning parameters could be enhanced the piezoelectric properties of these materials. The main objective of this paper is applying the Genetic Algorithm (GA) to determine the optimum condition of solution parameters and processing conditions based on the desired diameter size of PVDF fibers to produce the fibers without any structural faults. In this method, The Fitness function was determined by a simple analytical model presented by Fridrikh. Toward approving the GA results the experimental tests were done. the effect of four parameters such as flow rate of the polymer solution, electrospinning voltage, electrospinning distance and polymer concentration on the fiber formation and fiber diameter size of electrospun PVDF fibers have been explored by Scanning Electron Microscopy (SEM) to attest the accuracy of the model. Assessment of experimental and theoretical results show that electrospinning parameters determined by GA method leads to achieve desire fiber diameters. Because of time and energy consuming of electrospinning process, the GA method may be useful to achieve desired fiber diameter by determining electrospinning parameters for polymers prior to fiber production

Hibrit artık robot kolu kullanarak yüksek performanslı taşlama işlemi geliştirmesi.

Automatic grinding using robot manipulators, requires simultaneous control of the robot endpoint and force interaction between the robot and the constraint surface. In robotic grinding, surface quality can be increased by accurate estimation of grinding forces where significant tool and workpiece deflection occurs. Tool deflection during robotic grinding operation causes geometrical errors in the workpiece cross-section. Also, it makes controlling the grinding cutting depth difficult. Moreover small diameter of the tool in robotic grinding causes different behavior in the grinding process in comparison with the tools that are used by universal grinding machines. In this study, a robotic surface grinding force model is developed in order to predict the normal and tangential grinding forces. A physical model is used based on chip formation energy and sliding energy. To improve the model for robotic grinding operations, a refining term is added. In order to include the stiffness of the tool and setup in the force model, penetration tests are implemented and their results are used in refining term of the force model. The model coefficients are estimated using a linear regression technique. The proposed model is validated by comparing model outputs with experimentally obtained data. Evaluation of the test results demonstrates the effectiveness of the proposed model in predicting surface grinding forces. In this thesis, a method is proposed for calculation of the tool deflection in normal and tangential directions based on grinding force feedback in these directions. Based on calculated values, a real-time tool deflection compensation algorithm is developed and implemented. Implementing surface grinding with constant normal force is a well-known approach for improving surface quality. Tool deflection in the robotic grinding causes orientation between the force sensor reference frame and tool reference frame. This means that the measured normal and tangential forces by the sensor are not actual normal and tangential interaction forces between the tool and workpiece. In order to eliminate this problem, a resultant grinding force control strategy is designed and implemented for a parallel hexapod-robotic light abrasive surface grinding operation. Due to the nonlinear nature of the grinding operation, a supervised fuzzy controller is designed where the reference input is identified by the proposed grinding force model. Evaluation of the experimental results demonstrates significant improvement in grinding operation accuracy using the proposed resultant force control strategy in parallel with a real-time tool deflection compensation algorithm. The final aim of this thesis is to develop a posture optimization strategy for robotic grinding operation using 12 DOF hybrid redundant manipulator. The 12 DOF redundant hybrid manipulator of present study is composed of a 6 DOF serial ABB IRB2000 robot and a 6 DOF PI H-824 hexapod where the parallel hexapod is connected to the end of the serial ABB manipulator. Here the fifth joint (wrist) of the ABB serial manipulator is the weakest joint in the robot, so the computed torque of this joint is selected as the cost function. The aim is to minimize this factor by finding the best configuration of the hybrid manipulator using genetic algorithm approach. For such a purpose, a complete kinematic and dynamic model of the 12 DOF manipulator is developed where the output of the grinding force model is fed into the dynamic model as external reaction forces. The computed torque of the wrist joint is given to the optimization module and new configuration is generated by the module and is given to the dynamic model. This process continues until converge to the minimum computed torque value. Then the optimal configuration is chosen for the grinding operation. The evaluation of this posture optimization approach shows its great ability to decrease the necessary actuating torques of the redundant manipulator joints.Ph.D. - Doctoral Progra

Modelling of surface roughness based on geometrical parameters of woven fabrics

A novel model has been developed for the surface roughness evaluation of woven fabrics, based on fabric geometrical parameters. The model is developed based on the properties of twenty five groups of woven fabrics consisting of five various weave structures and five different weft densities. The output of the model is validated through a set of subjective roughness pair-comparison tests. The model output is found to be in accordance with the roughness scale value which is obtained from subjective tests, to a reasonable extent. The statistical analysis of roughness results shows that the effect of fabric structural parameters such as weave structure and weft density is significant in the confidence range of 95%. This model can be utilized for the prediction of the roughness behavior of various types of woven fabrics. Bearing in mind the influence of fabric surface roughness on the comfort and aesthetic properties of cloths, the usage of the model is a guide for selecting the suitable fabric for various end uses

Measurement of yarn density in woven fabrics using fringe projection moiré techniques

Fringe projection Moiré, a novel, accurate and fast technique with high repeatability, has been developed in order to measure the yarn density in woven fabrics. In the experimental set-up, collimated laser beams illuminate a Ronchi grating to be projected on a fabric. In case the density of projected lines and fabric becomes the same, the desired moiré pattern is observed on the fabric. As a result, the measurement of the distance between grating and fabric can guide us to find out fabric yarn density by using simple equations. In this regard, twenty five groups of shirting woven fabrics consisting of five weave structures and five different weft densities have been tested. The results show that there is a high correlation (R2 =0.9932) between the data obtained from the new and the conventional methods

Acetazolamide and Thyroid-Associated Ophthalmopathy; a Preliminary Tested Hypothesis in a TertiaryReferral Center

This study evaluated the effect of acetazolamide on thyroid-associated ophthalmopathy (TAO). Patients with a VISA classification index equal to or more than four were enrolled in the study and were randomly assigned into two groups. In both groups, treatment was initiated using prednisolone. Patients in the case group received acetazolamide tablets 250 mg daily in addition to prednisolone. Three months later, the VISA inflammatory score of patients in both groups were determined. Subsequent to intervention with acetazolamide, the VISA inflammatory score of patients in the case group were reduced as follows; orbital pain (57.1% versus 41.7%, P=0.736), eyelid edema (42.8% versus 27.1%, P=0.67), chemosis (53.3% versus 33%, P=0.31), injection of the eyelids (60% versus 41.6%, P=0.342), and conjunctival injection (50% versus 46.13%, P=0.73). However, these reductions were not statistically significant when compared with those observed in the control group (P=0.246). In conclusion, the effect of acetazolamide on all the parameters of the VISA inflammatory score was examined independently. All patients in the case group revealed a reduction in VISA inflammatory score following intervention. However, these reductions were not statistically significant. Further studies with large sample sizes are required

Effect of weft yarn laying on tensile properties of weft-inserted knitted fabrics

To investigate whether the combination of tuck and miss stitches can be used as an alternative method to produce weft-inserted fabrics, in cases where the weft knitting machine is not equipped with a weft insertion system, straight yarns with various densities and arrangements have been inserted in the course direction of rib weft knitted fabrics. The results of tensile tests in the course and wale directions denote that the use of straight yarns increases the tensile strength and tensile strain of the fabric in both directions, while the elastic modulus increases in the course direction. Furthermore, increasing the straight yarn density leads to an increase in the tensile strength and elastic modulus and a decrease in the tensile strain in both directions. Eventually, since the weft yarn arrangement has no significant effect on the fabric tensile strength and elastic modulus, this method can be used as an alternative method to produce weft-inserted fabrics

Acetazolamide and Thyroid-Associated Ophthalmopathy; a Preliminary Tested Hypothesis in a TertiaryReferral Center

This study evaluated the effect of acetazolamide on thyroid-associated ophthalmopathy (TAO). Patients with a VISA classification index equal to or more than four were enrolled in the study and were randomly assigned into two groups. In both groups, treatment was initiated using prednisolone. Patients in the case group received acetazolamide tablets 250 mg daily in addition to prednisolone. Three months later, the VISA inflammatory score of patients in both groups were determined. Subsequent to intervention with acetazolamide, the VISA inflammatory score of patients in the case group were reduced as follows; orbital pain (57.1% versus 41.7%, P=0.736), eyelid edema (42.8% versus 27.1%, P=0.67), chemosis (53.3% versus 33%, P=0.31), injection of the eyelids (60% versus 41.6%, P=0.342), and conjunctival injection (50% versus 46.13%, P=0.73). However, these reductions were not statistically significant when compared with those observed in the control group (P=0.246). In conclusion, the effect of acetazolamide on all the parameters of the VISA inflammatory score was examined independently. All patients in the case group revealed a reduction in VISA inflammatory score following intervention. However, these reductions were not statistically significant. Further studies with large sample sizes are required

Social capital and related factors in Western Iran students

Abstract  Background & Aim: Social capital involves a set of norms available in social systems which improves the interaction between people and reduces the costs of interactions and communications. The purpose of this research was to Study of the social capital of the students of Kurdistan University of Medical Sciences and its related factors, 2017. Material and Methods: The method of this study was descriptive survey method. The statistical community of this study included all students of Kurdistan University of Medical Sciences  among whom 378 students were selected randomly as samples of the study. Delaviz questionnaire of social capital was employed for data collection and data analysis was performed using Spss software,  descriptive statistics(mean, standard deviation) and Inferential statistics (U-Mann Whitney, Kruskal-Wallis). Results: The means of social capital was 70.56±10/88. Minimum and maximum mean was measured for “participation in local community” and “group participation”. In this study, There were significant associations between social capital with gender, field of study and and marital status.(p<0/01). Conclusion: Social capital as the most important factor for people dealing with stressful situations known, and can facilitate problem tolerate for them. Social capital as an important factor, can help the health and life satisfaction of students

Experimental and theoretical investigation of hollow polyester fibers effect on impact behavior of composites

In this paper, the effect of utilizing hollow polyester fibers as reinforcement in composite material in comparison with solids is investigated. The three-point bending impact test is carried out to study the impact behavior and mode of failure of composites. After that, the finite element method is used for theoretical investigation and modeling the behavior of two different reinforced composites during impact tests. It was found that the fiber–matrix interface failure is the most dominant mode of failure and the crack was initiated at the middle of the bottom surface of composites. It was also found that the impact resistance of the hollow fiber composite is more than the others. Theoretical results showed good correlation with experimental results as well. The stress distribution and the maximum value of strain energy density was found as two factors which lead to improvement in the impact behavior of hollow fiber composites