Experimental study on perfomance of wind catcher in tropical climate

Today, the knowledge of using natural ventilation in buildings with consideration of traditional architecture of different areas, has become an important factor to consider in the buildings. The focus is on increasing the quality of space regarding to climate and environmental parameters. Iran is a country with vast and different types of climate and each one has come with it's own harmonic way and response in architecture. In these study conventional traditional buildings exposed to the hot and humid weather in the northern coast of Persian Gulf and Oman Sea is considered. The wind catcher is widely applied in these areas to enhance the natural ventilation in buildings. Studying the regional measures of the local expert architects can contribute to a suitable building design for such a climate. This paper aims to study how the wind catcher works by the wind-tunnel testing and CFD simulations. The main objective of this research is to discover how a wind catcher works by considering climate situations of a tropical region. The results show that increasing the height optimizes a wind catcher's performance by taking other appropriate variables. Furthermore, this study shows that the proposed system, even at relatively low speed outdoor wind, is able to create ventilation in a residential unit. According to the results of the wind-tunnel test and CFD simulations, the wind catcher can be used in hot and humid tropical areas to help create thermal comfort in green buildings by increasing the natural ventilation

The Effectiveness Of Incidental Teaching Of Grammar To Iranian Students

This article reports the results of a study and a pilot study.  The ‘study’ considers the effectiveness of incidental teaching of grammar in a learning class of English As A Second Language by Persian speaking students.  The ‘pilot study’ examines the students’ attitudes toward the incidental learning of grammar from the perspective of field dependent/independent.   The subjects of this study are two groups of EFL learners, a total of 30 students studying at Sabzevar Payam Noor University, Iran.  English proficiency was measured by the TOEFL and an oral test of communicative competence.  Grammar is presented in two series of lessons. The first, a series of ten grammar lessons, provides an intensive review of grammatical points for beginning ESL students. These lessons assume a low vocabulary level, include a simple grammatical generalization, and provide extensive practice of specific grammar points using a wide variety of exercises. A built-in review is provided for items that are missed in each exercise. The second series, six advanced grammar lessons, provides extensive reinforcement and practice of a wide range of advanced grammar points. Each lesson consists of at least four mechanical exercises, including substitution, transformation, question/answer, and fill-in-the-blank drills.  The focus in this study is on learning grammar, in general, and passive voice, in particular.  A pre-test is administered to be certain. This test consists of 60 multiple-choice questions.  The subjects fortunately are almost at the same level; the averages are very close.  The subjects were divided into two groups: control and experimental. Then the easy texts, which include the grammatical points, are taught incidentally to the experimental group, whereas explicitly to the control group. A test is carried out for the groups.  Then in the following term, the same groups are taught the advance materials followed by a test. The results indicate that the use of an incidental method of teaching does not show a significant priority over the explicit one.  In reality, the control group does better, especially with the advanced materials.  Concerning the pilot study, a questionnaire is distributed among the subjects to identify the field dependent/independent ones. The aim of this pilot study is to identify what kinds of students are more interested in incidental learning of grammar.  Five students are selected from each group.   The analysis of the data concerning their reception of the method of teaching and the outcome of the groups is carried out. The study does not show a significant difference between field dependent/independent students concerning incidental learning. &nbsp

Investigation the solidification of Al-4.8 wt.%Cu alloy at different cooling rate by computer-aided cooling curve analysis

Depending on the casting conditions and alloy composition, microstructure and properties of the aluminium alloys will be different. There are many techniques available for investigating the solidification of metals and alloys. In recent years computer-aided cooling curve analysis (CA-CCA) has been used to determine thermophysical properties of alloys, latent heat and solid fraction. The aim of this study was to investigate the effect of cooling rate on the structural features of Al-4.8 wt.%Cu alloy by thermal analysis of cooling curves. To do this, Al-4.8 wt.%Cu alloy was melted and solidified applying 0.04, 0.42, and 1.08 °C/sec cooling rates. The temperature of the samples was recorded using a K thermocouple and a data acquisition system connected to a PC. It was found that the formation temperatures of various thermal parameters such as (liquidus, solidus and eutectic temperatures) are shifting by increasing of cooling rate from 0.04 °C/sec to 1.08 °C/sec. The structural results show that grain size and secondary dendrite arm spacing decreased by increasing of cooling rate.  http://dx.doi.org/10.5937/metmateng1402107

Cooling curve analysis in binary Al-Cu alloys: Part I- Effect of cooling rate and copper content on the eutectic formation

There are many techniques available for investigating the solidification of metals and alloys. In recent years computer-aided cooling curve analysis (CA-CCA) has been used to determine thermo-physical properties of alloys, latent heat and solid fraction. In this study, the effect of cooling rate and copper addition was taken into consideration in non- equilibrium eutectic transformation of binary Al- Cu melt via cooling curve analysis. For this purpose, melts with different copper weight percent of 2.2, 3.7 and 4.8 were prepared and cooled in controlled rates of 0.04 and 0.42 °C/s. Results show that, latent heat of alloy highly depends upon the post- solidification cooling rate and composition. As copper content of alloy and cooling rate increase, achieved nonequilibrium eutectic phase increases that leads to release of high amount of latent heat and appearing of second deviation in cooling curve. This deviation can be seen in first time derivative curve in the form of a definite peak

Tailoring sorption properties of nano-sized multilayer structured magnesium for hydrogen storage

To tailor the hydrogen sorption properties of magnesium, improve its poor kinetics and alter its thermodynamics properties, sputtered multilayer Mg-based thin films were prepared in which Mg layers were confined by AlTi layers. Multilayer samples of different Mg thickness showed relatively long activation periods compared to the conventional co-sputtered alloys thin films. This activation period is attributed to the formation of voids and new surfaces which facilitate hydrogen transportation and its interaction with base metal. It has been found that the cyclability performance of materials is strictly connected to the stability of microstructure and resistance of multilayer structure to grain growth. At a certain Mg:AlTi thickness ratio (10:2), sintering of Mg layer could be prevented and long cyclability over 250 cycles has been achieved. Multilayers of few nm Mg thicknesses possess equilibrium pressures higher than pure Mg and the plateau pressure is a function of Mg thickness

Fabrication of Iron Aluminide Coatings (Fe3Al and FeAl3) on Steel Substrate by Self-Propagating High Temperature Synthesis (SHS) Process

Iron aluminides (Fe3Al and FeAl3) coatings were fabricated on a steel substrate by self-propagating high temperature synthesis (SHS) method. Raw materials, Fe and Al powders, were mixed at two different stoichiometry ratios (3:1 and 1:3). The mixtures and the substrate were placed in a furnace at 950 °C to ignite the SHS process. Coating phases were investigated using X-ray diffraction (XRD) and Energy Dispersive Spectroscopy (EDS). The microstructure of the coatings was analyzed with optical microscopy (OM) and scanning electron microscopy (SEM). The results confirmed that it is possible to produce Fe3Al and FeAl3 coatings on steel substrate using SHS method. In addition, the results show that the coatings were composed of two different phases and their microstructures were non-porous and dense. Wear resistance of the coatings were higher than that of the substrate

Cooling curve analysis in binary Al-Cu alloys: Part II- Effect of Cooling Rate and Grain Refinement on The Thermal and Thermodynamic Characteristics

The Al-Cu alloys have been widely used in aerospace, automobile, and airplane applications. Generally Al-Ti and Al-Ti-B master alloys are added to the aluminium alloys for grain refinement. The cooling curve analysis (CCA) has been used extensively in metal casting industry to predict microstructure constituents, grain refinement and to calculate the latent heat of solidification. The aim of this study is to investigate the effect of cooling rate and grain refinement on the thermal and thermodynamic characteristics of Al-Cu alloys by cooling curve analysis. To do this, Al-Cu alloys containing 3.7, and 4.8 wt.% Cu were melted and solidified with 0.04, 0.19, 0.42, and 1.08 K/s cooling rates. The temperature of the samples was recorded using a K thermocouple and a data acquisition system connected to a PC. Some samples were Grain refined by Al-5Ti-1B to see the effect of grain refinement on the aforementioned properties. The results show that, in a well refined alloy, nucleation will occur in a shorter time, and a undercooling approximately decreases to zero. The other results show that, with considering the cooling rate being around 0.1 °C/s, the Newtonian method is efficient in calculating the latent heat of solidification

Grain size control in al-4.8 wt.% Cu alloy by computeraided cooling curve analysis

Generally Al–Ti and Al–Ti–B master alloys are added to the aluminium alloys for grain refinement. The cooling curve analysis (CCA) has been used extensively in metal casting industry to predict microstructure constituents, grain refinement and to calculate the latent heat of solidification. The aim of this study was to investigate the effect of grain refinement on the grain size of Al-4.8 wt.%Cu alloy by cooling curve analysis. To do this, alloy was grain refined by different amount of Al-5Ti-1B master alloy and all samples were solidified at constant cooling rate of 0.19 ℃/s. The temperature of the samples was recorded using a K thermocouple and a data acquisition system connected to a PC. The results show that the segregating power of Ti is very high and it segregates to the nucleant–liquid interface which leads to constitutional supercooling within which other nucleant particles get activated for nucleation. Other results show that with considering the changes in the primary undercooling (ΔTRU) as the main factor to determine the effectiveness of grain refinement process, it was found that by grain refinement, the value of undercooling decrease was approximately zero. http://dx.doi.org/10.5937/metmateng1403183

Causal analysis of safety risk perception of Iranian coal mining workers using Fuzzy Delphi and DEMATEL

Underground coal mines, one of the most dangerous work environments, have experienced accidents and disasters. One of the main reasons for those unsafe events is the workers’ poor understanding of the hazards and risks of working in this work environment. Therefore, the present study aims to identify factors affecting the safety risk perception of underground coal mine workers in Iran and investigate their cause-and-effect relationships. By reviewing the literature, 40 variables were identified in five categories: individual, organizational, environmental, task, and external factors. The identified variables were ranked according to the expert group’s opinion in the form of a fuzzy Delphi study regarding their effects on risk perception. In the next step, 23 variables were selected to investigate the cause-and-effect relationships using the DEMATEL method. The study’s findings showed that organizational factors and some individual factors play a fundamental role in workers’ risk perception. The variables of safety culture, safety management style, and safety attitude had the most significant impact, and the variables of personal protective equipment and risk aversion had the smallest impact on workers’ risk perception. The present study’s findings can be used as a guideline to provide effective solutions for managers and workers in improving safety risk perception, subsequently reducing unsafe behaviors and increasing the safety status of underground coal mines.This research was funded by the KASHAN University of Medical Sciences and Health Services and grant number 140008257113.Peer ReviewedObjectius de Desenvolupament Sostenible::8 - Treball Decent i Creixement EconòmicPostprint (published version