Sharif Digital Repository

Main aim of this work was to obtain the harder zinc coating and increasing the anti corrosive properties by mean of adding SiO2 particles by electrophoretic method.
The coating was applied on the substrate surface by mean of electro co-deposition technique in three different electrolytes ethanol, methanol and water. The morphology of the coating in each electrolyte studied by scanning electron microscope (SEM).For the Zn/SiO2 coatings achieved in ethanol solvent the polarization and EIS tests was took place and found that for the Zn/SiO2 coating contain less than 10% SiO2 the corrosion rate decreased but for the coatings contains more than 10% SiO2 the paradox occurred because of the... 

Validation is an important enterprise especially when the test to be validated is a high-stakes one the results of which bring about life-changing implications for the candidates (Roever, 2001). Messick’s (1988) notion of construct irrelevant factors is pertinent in test validation. Demographic variables like gender, field of study and age can affect test results and interpretations. A fair test needs to be neutral when it comes to construct irrelevant factors such as gender. Differential Item Functioning is a way of making sure that the test does not favor one group of test takers over the others. The current study investigated differential item functioning (DIF) in terms of gender in the... 

The present study was conducted to examine the effect of explicit and implicit teaching of the speech acts of apologies and requests with 40 students. They were given a discourse completion test (DCT) which was designed by the researcher. The students came up with situations that embodied apologies and requests. After exemplar generation and likelihood investigation some 16 items were retained and used with students. The participants of the study consisted of two groups of implicit and explicit. The two groups were intact and randomization was not a possibility. The design was quasi-experimental. To investigate the relationship between grammatical competence and pragmatic competence, the... 

The present study was conducted to explore the effect of strategy based instruction and task based teaching on EFL learners’ production of apology and request speech acts and also to investigate the relationship between grammatical competence and speech act performance. To this end, 35 intermediate English language students that comprised two intact classes in a language institute participated in this study. A standard English proficiency test for intermediate level and a discourse completion task (DCT) were used to measure students’ grammatical competence and speech act production. DCT was used at the beginning of the study to ensure that the two classes were homogenous in terms of apology... 

Despite the proven advantages of alternative assessment including self- and peer assessment, there is still uncertainty about the accuracy of these techniques especially in Iran since little research has conducted in this area. To this aim, a total of 2261 evaluation sheets were collected to investigate 118 peer assessments and 48 self-assessments of oral presentations in comparison with their teacher assessments. The data were collected during four semesters in general English classes held in Sharif University of Technology. Students were supposed to make an oral presentation for at least twenty minutes on a topic of their interest, and were then rated by their teacher, themselves, and... 

Hydrogen sulfide, H2S, is a toxic gas and has detrimental effects on human health and the oil and gas industry. Therefore, its identification is very important. According to the devastating effects of this gas, then, the general mechanisms have been studied for gas detection. In addition, by highlighting the benefits of the multilayer nanostructure electrochemical sensors, an applicable and efficient method for the industrial production of these sensors has been investigated. In this regard, the sol-gel method is used to prepare the SnO2-CuO multilayer thin film and the advantages of this method was compared to PVD method. Also sensor properties of both deposition methods have been... 

The present research aims to examine the washback effect of TEFL M.A. entrance examination on university professors` and B.A English students` perceptions towards material preparation and instruction. With this end in view, a questionnaire and some interviews were used to gather information about the issue at point. The questionnaire includes a set of questions developed to help gain insight into the research questions. The interviews were held with B.A English state-university professors to provide additional and complementary information. The research tools enjoy expert judgment in terms of validity and as for the reliability, the questionnaire was proved to have an acceptable degree of... 

The present study compares the reaction times in processing unambiguous sentences with three ambiguous statements of lexical, grouping and functional as well as garden path sentences. To this end, a special computer program was developed with the accuracy of micro seconds. Furthermore, a set of 25 items was prepared with acceptable levels of reliability and validity. Forty seven highly proficient subjects, all undergraduate students of Air Traffic Control, participated in this study. The results of the study showed no significant difference between the reaction times of grouping and functional ambiguities but garden path sentences showed the greatest difference with the other groups. All... 

The present study aims at examining interval scaling and magnitude estimation in grammaticality judgment tests in terms of reliability and validity. It also explores the probable impact of response formats on the participants’ performance. 30 Engineering students at Sharif university of Technology participated in this research. The instrument of the research is a grammaticality judgment test developed by Ellis (1990).Two computer-based programs were made in order to assess the two mentioned response formats in grammaticality judgment test. At the first phase of the study, the participants responded to the interval format and after an interval of one month, they attempted the second response... 

The relationship between travel behavior and Built Environment has been context of variety of research during past decades. Many modern urban development theories such as new-urbanism and smart growth are commonly based on interactions between these two concepts. This research is aiming to analyze the effects of built environment on household trip generation, mode and destination choice as specific indices of travel behavior, based on travel diary data of Shiraz city. Multiple Linear Regression and Multinomial Logit Model concepts are used to analyze aforementioned travel behaviors in two levels. Base models predict socio-economic variables importance and expanded models are used to test... 

Translation quality assessment (TQA) as a systematic field of inquiry has been under scholarly investigation over the past decades. In spite of the challenges appeared in the path to success, theoretical and practical developments have already been made in translation studies. One of the unsettled and challenging problems concerning translation assessment, yet, is the subjectivity that is inherent in the process of scoring test-takers’ translation performances. In the absence of any granular objective criteria which includes all the subcomponents of translation as a multi-layer rather than unitary construct, the raters inevitably bring their intuition and will to the act of measurement.... 

Given the significance of providing any logical and empirical pieces of evidence to “support the assentation that a test measures the construct as defined and nothing else” (Ary et al., 2013, p. 248), numerous studies have been conducted to investigate construct validity, adopting various approaches. However, there are few studies employing the experimental approach to validation. The current study is aimed at obtaining statistically persuading evidence to answer the question regarding the adequacy of the experimental approach to construct validation, drawing upon the concept of advertising literacy as the construct of the researcher’s concern. To meet this end, the researcher, having... 

In the last decades, Reaction Time research has been extended to cognitive science and more specifically human information-processing research and has gained momentum (Shim, 1996). The present study examined the reaction time in processing marked and unmarked structures with regard to the four types of conditionals (considered as unmarked, less marked, marked and strongly markedness, respectively) and prepositions (preposition pied piping that is considered as unmarked and preposition stranding as marked). To this end, two softwares were developed for which the items relating to conditionals were chosen from the Bernet’s test (1985) and the ones pertinent to prepositions were taken from... 

Today global network of transportation is mainstream for economic growth and business development, growth in population made a need in optimization of using routes in global air transportation network, research shows cooperating with Airline Alliances is beneficial and gives much more freedom to their members in schedule planning and pricing as well as common interest in market share in international market. Joining an alliance affects decision making process of airline (e.g. fleet design, scheduling, route planning and crew assignment) in competitive market. Difficulty and complexity of evaluation in cooperative decision making that needs research to develop a model to evaluate decision... 

This thesis presents turbulent partially premixed combustion modeling behind a bluff-body by using the Flamelet Generated Manifold. The objective of the present work is to develop a 4D FGM program to simulate partially premixed combustion at a reasonable computational cost. Pre-tabulated data of this manifold is obtained by using a correlated joint PDF. An in-house code is developed to build a pre-tabulated library in conjunction with a correlated PDF. Also, an exclusive OpenFOAM solver is created by employing the PIMPLE algorithm. This solver provides the link of the computational domain with the pre-tabulated chemistry. This program is used to simulate Cambridge-Sandia stratified burner... 

Due to daily decrease of fossil energy resources, increase of environmental pollution which is included of toxic and greenhouse gases, and extensive growing rate of demands in transportation industry, especially vehicle industry, developing solutions in using fuel cells are vital for this industry in our country. Fuel cells are green, efficient and also powerful energy generators. According to potential advantages of fuel cells, structure, performance, benefits and also types of fuel cells are introduced as a desired energy resource. Indentifying existing choices of energy generators and ranking them using MCDM (Multi-Criteria Decision Making) technique was the first step to perform a... 

The present research aims to examine the influence of response format on the reliability and validity of grammaticality judgment tests, which will also reveal some facts about the superiority of each format. To this end, the grammaticality judgment (GJ) test developed by Gass (1994) was selected as the instrument of the study, which was manipulated in terms of the response format while the original items remained intact. Thus, in the first phase of the study, a multiple-choice GJ test (MCGJT) was constructed to be compared with the traditional form, i.e., the dichotomous type (DGJT). In an interval of a month, the two tests were administered to a group of 110 engineering-major BS students at... 

Today’s growing interest to the underwater explorations and navigations demands to design appropriate underwater communication methods and systems. However, radio frequencies which are widely being used in free space communications, can’t be a good candidate for underwater wireless communications, due to their sever attenuation in water. On the other hand, underwater acoustic communication has been widely studied and implemented in the past decades, inspired by suitable propagation of acoustic waves through the underwater medium. Nevertheless, acoustic communication systems have limited bandwidth, lower propagation speed and lower security than optical counterparts, which suggests underwater... 

Nowadays, economical extraction of oil and gas, and their products is an important issue for many countries. Up to now, vertical wells have been used for oil extraction but some wells exist that they cannot be reached by using vertical drilling; for example the wells under a sea. Therefore, this makes the governments and scientists determined to find a new way to reach them. Horizontal drilling is one of the new ways to reach such worthy wells. In this project, dynamics of the horizontal drill string is studied. Then, according to the forces that affect the dynamics of drilling, its vibration is analyzed. After finding the boundary conditions and normal modes of the system with using mode...