Sharif Digital Repository

For the preliminary design of isolated structures, it is necessary to select the appropriate damping ratios in each mode. The inherent modal damping in this type of structures is small. On the contrary, a significant value of damping is induced by dampers in isolator system into structural modes. The purpose of this study is to determine the Modal damping ratios in isolated structures. In this regard, shear structures of 2 to 10 floors with linear behavior in both superstructure and isolation level have been analyzed. The Structures have been modeled taking advantage of OpenSees. Samples are analyzed under sinusoidal loading applied to each floor. In order to achieve modal damping, an... 

In recent years, we have seen the proliferation of real-time and time-dependent systems. They have increased both in number and in complexity. Due to their increasing complexity, we need to model them and become assured of their correctness. Several formalisms have been devised for time-dependent systems. They include timed automaton and timed extensions of Petri nets. Our focus is on timed extension of activity networks and its model checking. Activity networksare powerful formalisms which allow designers to model the system in a natural, small and conceivable manner. This way, timed extension of activity networks can greatly help modelers. In this thesis, we propose a method to specify the... 

The purpose of this research is to investigate the seismic behavior of plane moment resisting frame consisting of steel-concrete columns and steel I beams utilizing fragility curves. Due to the great influence of the column type in seismic performance of structure. To reach an optimal system, different types of steel-concrete composite columns has been used in the models and the fragility curve of each one is compared. Steel-Concrete composite columns can be divided into three types: (1) concrete filled steel tube (CFT), (2) steel reinforced concrete (SRC) and (3) new combinations of (1) and (2). Due to the abundance of the use of concrete filled steel tube (CFT) and steel reinforced... 

Estimating the life-time of electronic devices has always been an important issue in their mass production. Nowadays, electronic chips are widely used due to technological advances and due to their smaller size. They may be more likely to break down because of their complexity. Therefore, estimating their life-time has received much attention. In the first chapters of this thesis, the concepts and standards that exist in the field of reliability and the life expectancy of electronic devices are discussed. There are many reasons for chip failure, which are beyond the scope of this thesis but what is known as the most important cause of failure which is named electromigration has been... 

This paper examines the impact of Ramadan fasting hours on stock market returns across 59 countries during the period 1980–2011. Exploiting cross-country variation in geographic latitude and daylight duration as an exogenous source of fasting intensity, we identify behavioral mechanisms underlying market performance during Ramadan. The results indicate that longer fasting hours are generally associated with lower monthly and annual returns. However, in Muslim-majority countries, this adverse effect is mitigated and, in some cases, reversed into positive returns. Seasonal analyses further reveal that the positive impact is more pronounced during summer months, and that extended fasting hours... 

A gas cyclone is a fixed mechanical device that uses centrifugal force to separate solid particles from gas. Gas containing particles is brought tangentially into the cyclone. This results in the development of a vortex, which applies strong centrifugal forces to the particles. The larger particles move toward the outer wall of the system as a result of centrifugal forces. gases spiral down from a tangential inlet towards the conical section, where the flow is reversed and the particles are collected in a hopper. The gas phase then proceeds upward in an inner vortex towards the gas exit via the vortex finder.
In this study swirling flow of two-phase gas-solid in cyclone separator is... 

Liquid-infused surfaces (LISs) reveal promising performance in improving condensation due to their ability to create a surface with a low contact angle (CA) that is suitable for nucleation rate, and low contact angle hysteresis (CAH), which allows for easy shedding. However, these surfaces have been limited in practical application due to issues with durability and scalability. Additionally, creating durable surfaces has been expensive and poses risks due to using specific chemicals. In this study, aluminum samples covered with silicone oils of various viscosities and decamethylcyclopentasiloxane (D5) are exposed to ultraviolet (UV) light to produce a durable and low-cost 1-D LIS that does... 

Laufer and Hulstijn (2001) proposed the Task-Induced Involvement Load Hypothesis stating that in the retention of new words in an incidental context, tasks with higher involvement load will be more effective than tasks with lower involvement load. The present study aimed to examine whether the retention of vocabulary is enhanced with an increase in the amount of task-induced involvement load in an intentional learning environment. Moreover, it was investigated whether proficiency level of learners had a role in the effectiveness of the vocabulary tasks with different involvement loads. Four groups of university students, male and female, participated in the study. They were given a TOEFL... 

Self-regulated learning, though having swept educational psychology's literature like a tidal wave (Boekaerts, 1999), and also, compared to other constructs such as metacognition and learning strategies, has remained comparatively uncharted in L2 research. One preliminary step to chart this concept is to develop questionnaires for it. With these and other things in mind, the principal purpose of this study was to develop a questionnaire in English and Persian to measure self-regulated language learning capacity and behavior of Iranian EFL learners. The development of the questionnaire was guided by two pilots (412 participants), content validation through expert judgment, cognitive... 

Regardless of the extensive research on different aspects of vocabulary and the great emphasis that leading scholars (Meara, 1996; Nation, 990; Read, 1988) placed on the significance of the number of words a learner knows as a substantial component in language learning and vocabulary learning, few investigations have been conducted regarding the size of the vocabulary each language learner knows (Nation, 2012). In addition, Nation (2012) debates the need to combine modern technology and language testing. Therefore, it is necessary to provide innovative methods of testing this knowledge. The present study developed the Computerized Adaptive Test (CAT) of Nation and Beglar’s (2007) Vocabulary... 

A power transmission system includes transmission lines that are interconnected for economic and security reasons. Power systems are often prone to faults at the transmission level, since transmission lines are spread over vast geographical areas. Being the most serious events in power systems, blackouts are often initiated by a fault and a sequence of events afterward leads to partial or complete power outage. In this condition, fault diagnosis is the first step for power system restoration. In this research work, a new approach utilizing impedance-based fault location is introduced for fault diagnosis. By developing wide-area measurements in the context of smart grids, accurate... 

Internet of Things (IoT) is one of the most emerging fields in the computer science context. It is predicted that more than 9 billion devices will be connected to IoT networks by 2025. Considering the specifications of IoT devices such as low battery capacity and small memory, these networks face major challenges in energy consumption and reliability. One of the most important elements which have an indisputable effect on network efficiency is routing protocol. In this manner, IETF presented RPL in 2012. It is designed to create a robust network among IoT devices.Although RPL performs well in static networks, it is not designed originally for mobile networks and it has serious flaws in that... 

In conventional method of modeling and design of structures it is assumed that structures are fixedly supported, however, this assumption is generally far from reality; because, not only the majority of buildings’ bases are not stiff enough to suppose them rigid, but also if their foundations are shallow there exist no piles underneath them, they may separate from their bases – the event which is called foundation uplift. Although according to past studies permission of foundation uplift as well as incorporation of base flexibility may markedly affect any structure’s dynamic response, is spite of about half a century which has elapsed since the beginning of these studies, it seems that still...