Proposed Model for Stress-strain Behavior of Fly Ash Concrete Under the Freezing and Thawing Cycles

Fly ash is a supplementary cement material using instead of Portland cement in concrete. Using this material concludes to less emission of greenhouse gas and less water demand of concrete. In this paper, an experimental investigation was carried out on compressive stress–strain behavior of three groups of concrete specimens with different water/cement ratios (0.45, 0.5 and 0.55), containing 0, 10, 20, 30 and 40 percent of fly ash (by weight), after subjecting to freezing and thawing cycles. 0, 45, 100 and 150 cycles of freezing and thawing were applied on these specimens according to ASTM C666 and the results presented. Numerical models for the stress–strain behavior of these frozen-thawed concrete were developed and compared with the available experimental data. Results show that the maximum compressive strength of these concrete specimens exposing cycles of freezing and thawing is gained by using about 10 % of fly ash. Moreover, there is a good agreement between the proposed models and test results and the difference is less than 5 %

Finite Element Analysis on Reinforced Concrete Columns Strengthened by ECC Jacketing under Eccentric Compressive Load

Engineered cementitious composite (ECC) can be used for strengthening of concrete columns due to its similar structure and suitable connection to normal concrete and its special tension behavior. In this study, to analyse the columns, finite element (FE) method was used after verification by experimental results. Reference column was strengthened by normal concrete and ECC jacketing. The effects of type of jacket material, longitudinal reinforcement, compressive stress and ultimate tensile strain of ECC on variations of eccentric load-bending moment (P-M) interaction curves were investigated. Results showed that the use of ECC instead of normal concrete can increase load carrying capacity of strengthened column, due to tensile strain hardening behavior of this material. It was found that, amount of this increase depends on eccentricity of eccentric load and varying from 0.4-23%. In ECC jacketing, tensile cracks are continuous, but in concrete jacketing, there were discrete cracks and more quantity of damages. Due to higher load carrying capacity and better distribution of tensile cracks in ECC jacketing than normal concrete jacketing, the use of ECC is suitable for strengthening of reinforced concrete columns. Load carrying capacity of columns under concentric load and pure bending moment were calculated by theoretical method and the results were compared with FE

Efficient filtration system for paraffin-catalyst slurry separation

The filtration efficiency for separating liquid paraffin (or water) from a slurry consisting of 25 weight% spherical alumina in a Slurry Bubble Column Reactor (SBCR) comprised of a cylindrical tube of 10 cm diameter and 150 cm length was studied. Various differential pressures (ΔP) were applied to two separate tubular sintered metal stainless steel filter elements with nominal pore size of 4 and 16μm. The experimental results disclosed that the rate of filtrations increased on applying higher differential pressure to the filter element. Albeit this phenomenon is limited to moderate ΔPs and for ΔP more than 1 bar is neither harmful nor helpful. The highest filtration rates at ΔPs higher than 1 bar were 170 and 248 ml/minute for 4 and 16μm respectively. Using water as the liquid in slurry the rate of filtration enhanced to 4 folds, and this issue reveals impact of viscosity on filtration efficiency clearly. In all situations, the total amount of particles present in the filtrate part never exceeded a few parts per million (ppm). The statistical analysis of the SEM image of the filtrate indicated that by applying higher pressure difference to the filter element the frequency percent of larger particle size increases. The operation of filter cake removing was performed with back flashing of 300 ml of clean liquid with pressures of 3-5 bar of N2 gas

Wave Profile for Current Bearing Lightning Strokes

The propagation of breakdown waves in a gas, which is primarily driven by electron gas pressure, is described by a one-dimensional, steady-state, three-component (electrons, ions, and neutral particles) fluid model. This study will involve waves propagating in the opposite direction of the electric field force on electrons (anti-force waves—lightning return stroke) only. We consider the electron gas partial pressure to be much larger than that of the other species and the waves to have a shock front. Our set of equations consists of the equations of conservation of the flux of mass, momentum, and energy coupled with the Poisson’s equation. The set of equations is referred to as the electron fluid dynamical equations. For breakdown waves with a significant current behind the shock front, the set of electron fluid dynamical equations and also the boundary condition on electron temperature need to be modified. For a range of experimentally measured current values and a range of possible wave speeds, we will present the method of solution of the set of electron fluid dynamical equations and also the wave profile for electric field, electron velocity, electron temperature, and number density, as well as the ionization rate within the dynamical transition region of the wave

Mechanical and Durability Properties of Sustainable Self-compacting Concrete with Waste Glass Powder and Silica Fume

Environmental protection approach has caused to ignore the conditions and the possibility of using solid waste as a substitute for concrete. In this research, the effect of glass powder in percentages of 0-30 (in steps of 7.5%) and micro-silica (10% as a constant) as a substitute for cement is investigated on efficiency, compressive strength, tensile strength, and bending strength. surface water absorption, capillary water absorption, and freeze/thaw cycle are paid. The results showed that the use of glass powder leads to increases the fluidity and properties of fresh concrete. The mechanical parameters decrease slightly when 30% of cement is replaced with glass powder

Behavior of large-scale bracing system in tall buildings subjected to earthquake loads

Bracing is a highly efficient and economical method of resisting of lateral forces in a steel structure. The most common types of bracing are those that form a fully triangulated vertical truss. These include the concentric and eccentric braced types. In high-rise buildings, the location and number of bracings is an important limitation to the architectural plan. A similar scheme has been used in larger scale spanning multiple stories and bays in tall buildings which is called large-scale bracing system. Large-scale bracing (LSB) is a particular form of a space truss. It consists of multiple diagonal elements that form a diagonal grid on the face of the structure. In this paper, a 20 story steel frame with different arrangement of bracing systems is analyzed. Linear and static nonlinear (push-over) analyses are carried out and the results presented here. Analytical results show that, the large-scale bracing is more adequate system under the lateral loads. Using LSB in tall buildings, decreases the lateral displacement, drift ratio, uplift forces in foundation and increases the ductility and shear absorption percent of the bracing system. Moreover, the stress ratios in the structural members of LSB system are less than the relevant values in other bracing systems

A Pragmatic Analysis of the Translation of the Quranic Discourse Marker Thumma in Kurdish and Persian Parallel Corpora

Communicative and natural processing of language in the world of translation is substantiated through simultaneous decoding and encoding of information in the source and target languages. The researchers analy‌zed pragmatic strategies and approaches undertaken by the Persian and Kurdish translators of the Quranic discourse marker thumma. The source text corpus was selected randomly and the target text parallel corpora were selected based on purposive sampling. Theoretical perspectives in pragmatics and translation were employed in the analysis of parallel corpora in this investigation. The results revealed that various types and combinations of the Kurdish and Persian temporal discourse markers were utilized by these translators. Moreover, other Kurdish and Persian elaborative, contrastive, and inferential discourse markers were also used in rendering the discourse marker thumma in the Quran. This dynamic approach to the construction of discourse was substantiated based on the realization of different conventions in the construction of discourse in different languages and cultures. This dynamic system in the construction of a proper discourse for the readers is verified based on the application of different theories in discourse analysis and pragmatics and the application of context and text-sensitive strategies in the process of translation. The characteristics, bases, and resources of these dynamic translation strategies are discussed based on pragmatic awareness rising in various aspects of translation education and some suggestions were offered in the application of the findings in syllabus design, translation evaluation, and rethinking of approaches in lexicography

THE RELATIONSHIP BETWEEN MANAGERS' LEADERSHIP STYLES IN PHYSICAL EDUCATION OFFICES UNIVERSITIES AND SPORT VOLUNTEERS' SATISFACTION

The purpose of the present study was to investigate the relationship between managers' leadership styles in physical education offices universities and sport volunteers' satisfaction. Statistical populations of this study included the whole volunteer students in sport associations of countries decimal zones universities. The sample of the study consisted of 231 volunteers who were selected by Morgan Table (n=231), which the results of 208 questionnaires were statistically analyzed. After verifying the validity of questionnaires by the experts, their reliability were calculated as (α=0.91 and α=0.88 respectively for leadership style and Satisfaction questionnaires by Cronbach's alpha coefficient in a pilot study). Data were analyzed with parametric tests at P<0.05. Results showed a positive significant relationship between transformational leadership style with volunteers' satisfaction (r=0.341, sig=0.001). There was no significant relationship between transactional leadership style and volunteers' satisfaction (P>0.05). Also, There was negative significant relationship between laissez-faire leadership style and volunteers' satisfaction (r= -0.355, sig=0.001). Furthermore, there was a significant difference between preferences of managers' leadership styles. Thus, transformational style (3.723+0.683) was in first and the transactional (3.476+0.572) and laissez-faire (2.827+0.833) styles were in next preferences. Also, from volunteer students' perspective, Satisfaction of acquiring experience, career and social were the most important dimensions, and material Satisfaction was the least important factor. According to research results, It seems that managers of Physical Education offices universities can increase the amount of volunteers' Satisfaction and provide background of their more and most effective attendance in sport association with transformational and inspiration leadership styles, appropriate incentive policies and converting sport association environment to a place in which easier accessibility to individuals' volunteer incentives becomes possible

Construction of Evaluative Meanings by Kurdish-Speaking Learners of English: A Comparison of High- and Low-Graded Argumentative Essays

Academic writing ability is an important goal that learners of English as a Second Language (ESL) or English as a Foreign Language (EFL) try to attain. While ESL students’ academic writings have been widely explored, owing to few studies investigating appraisal resources in EFL students’ argumentative writing, the gap still exists about EFL students’ academic writing. This study aimed to see how Kurdish-speaking learners of English employ appraisal resources in their writings. It further aimed to explore whether the appraisal framework can be utilized as an assessment scale for evaluating the students’ argumentative writing. To this end, the study investigated the argumentative essays written by 15 bilingual Kurdish-Iranian graduates of English within the framework of the appraisal theory. The instruments applied in this study consisted of a modified rating scale for assessing the essays in terms of the macrostructures exploited in them and the framework for the analysis of appraisal resources. Quantitative findings revealed high-graded essays employ more attitudinal items and fewer monoglossic resources than low-graded ones. Qualitatively, the high-graded essays articulated attitudinal values in nominal forms and sometimes in a backgrounded manner while these values were mostly presented by surge of feelings and in a foregrounded way in the low-graded essays. Regarding engagement, unlike the high-graded essays, the low-graded ones were poor in recognizing other voices and alternative positions. Inspired by the strength of the appraisal model evaluating writing, results suggest that high-graded essays are successful in positioning readers attitudinally and clarifying the ethical message to readers