Sharif Digital Repository

The human brain needs to create a model of data surrounding it continuously. To do so, handling the dynamics of information through communication between the brain regions is a critical step. Having a model of this procedure in the brain not only provides a clear explanation of how cognition occurs in the brain, but also enables us to have a better view of the cognition impairments in the brain. Surprise is a process in the brain that brings various cognitive abilities, including attention and memory, into practical use. Furthermore, these abilities are about manipulating the input information in an optimized way. Memory is the ability to store information arriving at a specific time.... 

In real-time systems, jobs that miss their deadline are considered worthless or ineffective. Nowadays, real-time applications (such as multimedia) that communicate through software-defined networks (SDN) are widely used and will continue to expand in the future. SDN is an emerging network architecture in which control plane is separated from data plane to manage it directly. In this research, we make changes to the controller and the switch used in such network to deliver real time packets or real-time flows (such as video) on time, as much as possible. As missed deadline packets are worthless and they waste bandwidth, dropping them is a solution. Moreover, the controller can drop flows that... 

The use of steel as one of the most widely used materials in the construction of structures is accompanied by problems and among them the problem of establishing stability in structure is important. To provide stability in the structure as a whole and for each of its elements, the new edition of the American Specification for Structural Steel Buildings, has introduced three general methods based on the elastic analysis. It includes, direct analysis method, effective length method and first-order analysis method. Each method has advantages and disadvantages. The present study is divided into two parts. The first part gives an overview of the behavior of structures and methods of determining... 

In this research the process of incomplete reduction of hematite low iron ore to magnetite in a fluidized bed reactor was investigated. Temperature, composition of reduction air, particle size, and stay time were investigated as effective parameters. In this way, temperatures of 560, 580, 600, 620 and 640 degrees of centigrade, input air with flows of 1.2, 1.3 and 1.4 l/s, particles size of 425-850 µm, 850 µm-1.4 mm, and 1.4-2 mm, stay times of 4, 8, 12, 16, and 20 min were used in this research. The reduced specimens were analyzed by XRD and chemical analysis. The results illustrated that increase of temperature, decrease of input air flow, decrease of particles size, and increase of stay... 

Accurate description of kinematics of continuum mechanics is essential in simulation of large deformation problems in solid mechanics. From the numerical viewpoint, two main approaches have been used for such description; the Lagrangian approach and the Eulerian approach. However, each of these approaches suffer from shortcomings which hinders their application in large deformation problems. A more general approach called the Arbitrary Lagrangian-Eulerian method (ALE) provides an opportunity to exploit the advantages of both Lagrangian and Eulerian approach, while avoiding their shortcoming. In an ALE analysis, the FE mesh is neither attached to the material nor fixed in space, necessarily.... 

Due to several reasons such as water deficiency and gradual reduce in water resources, dams had always been prominent during past centuries. Most of the dams have been built proximate to cities to provide water for drinking and industries thus, it’s vital to examine them in the aspects of safety factor and capacity to contain overflow. Failure of the dames should also studied considering different features such for instance sudden increment of stored water behind the dam as a result of gigantic floods, leakage in the body of soil dams, overflow in the dam crest due to insufficient functionality of spillway and etc. which could cause the failure of dams.
The main purpose of this thesis... 

Different causes in the exploration, production and transport of oil in the marine environment result in oil spill events. Since elimination of the probability of occurrence of spills is not possible, it is important to have a plan to control the risk of oil spills by optimal response. In this research, a general stucture is presented for the DSS required for oil spill response planning. This system can be used for evaluation of the effectiveness of response drills, and risk-based ranking of receptor areas and spill sources. Ranking based on risk is realized through probabilistic or stochastic risk assessment. The applicability of the proposed system is examined in differnet case studies in... 

Cold-formed steel sections are lightweight materials and suitable for building construction owing to their high structural performance. Conventionally, they are used as purlins and side rails in the building envelopes of industrial buildings. The most common sections are lipped C and Z sections, and the thickness typically ranges from 1.2 to 3.2 mm, and sections with yield strengths at 280, 350 and 450 MPa are commonly available. For connection design, codes of practice for design of cold-formed steel structures only provide design rules for the load carrying capacities of individual fastenings with bolts, screws and welds while no guidance on the structural behavior of connectors such as... 

Defining the structure of maps using local features is among the popular fields of study in mathematics. Therefore determining the structure of maps on rings which behave like derivations at idempotent-product elements has been getting attention recently. This subject is useful for examining the structure of rings and algebraic operators in both algebra and analysis as well. Suppose that R is a ring, d : R ! R is an additive map, z 2 R and d meets the condition below: 8a; b 2 R : d(ab) = ad(b) + d(a)b Therefore d is called a derivation on R. If for every a; b 2 R where ab = z, d(ab) = ad(b) + d(a)b then d behaves like a derivation at idempotent-product elements of ab = z. The main challenge... 

Natural gas (NG) has emerged as an alternative energy source in transportation sector as it provides clean combustion and hence lowers exhaust pollution. NG can be stored as an adsorbed phase in porous materials and is referred to ANG. The use of adsorbent materials for storing NG, at relatively low pressure (3.5–4 MPa), is a possibility for making ANG technology competitive with CNG. Among all adsorbents, carbon nanostructures with pore diameter (0.8-1.4 nm) has shown the highest adsorption capacity of natural gas. In the present study, cellulose has been used as the carbonaceous precursor and Activated Carbon (AC) has been prepared using hydrothermal carbonization of cellulose followed by... 

Hyperbranched copolymers are highly attractive due to their unique properties, such as tunable structure and surface functionality, making them versatile for applications in biotechnologies, pharmaceuticals, and materials engineering. Glycidol, as a reactive monomer with excellent biocompatibility, combined with sulfur, which enhances mechanical and chemical properties, represents a promising combination for hyperbranched copolymer synthesis. In this study, hyperbranched glycidol-sulfur copolymers were synthesized using cationic and anionic ring-opening polymerization methods. FT-IR analysis confirmed the successful incorporation of S-S bonds and sulfur-containing functional groups into the... 

A new types of architected cellular materials are those with negative poisoon’s ratio named auxetic. This materials indicate unormal behavior under different loads as if they were stretched in one direction, they also expanded in other directions and if pressure is exerted in one direction, they are compressed in all directions. Auxetic materials can improve mechanical properties such as shear strength, strength to weight ratio, thoghness, energy and vibration dissipation and crack expansion due to fatigue.The useful features of this material have been taken into account in a variety of industries, including the automotive industry, in the manufacture of parts such as body and bumper,... 

The low female labor force participation rate in the Iranian labor market relative to the global average and even to countries that do not differ significantly from the socio-economic characteristics of our country is one of the important questions of the Iranian labor market. In this study, we seek to answer the question of whether the economic participation rate of married women will increase if the gender gaps in wages, job findings and job losses among women and men are eliminated in the Iranian labor market. To answer this question using household expenditure and income data and labor force data, we show that between the two categories of occupations, in terms of the share of women's... 

Fatigue crack growth can have harmful effects on the reliability rotary machine. While an early warning to crack, can be used to extend the life of these expensive machines and increase reliability.Structural Vibration Condition Monitoring as a primary fault detection method, achieved to a lot amazing result and for this reason studies vibration behavior of cracked rotational shaft is a big issue for engineers of dynamic machine.In this research, first check the fault detection methods based on structural vibration condition monitoring, mode shape methods were extracted. Then by modeling rotational shaft in computer and creation of crack on it, fault detection quality of these methods have... 

It is important to provide an appropriate and economically method with technical and engineering considerations to stabilize excavated underground spaces. The necessity of this, especially for the construction of underground metro stations located in the cities which faces many problems, is more evident. In this research, it has been tried to introduce an optimal method according to the type of area for the construction of the underground station. In order to obtain stress and strain condition in structural elements and surface deformations due to different stages of excavating, numerical modeling in FLAC3D has been used. By examining the parameters that affect the sustainability of this... 

In the present study, the effects of increasing the value of shale gas production, either due to increased production or price increases, have been studied on economic variables such as employment, wage, property value and the number of births. In this regard, the data for each of these variables was used at the county level in the United States of America between 2000 and 2011. In order to estimate the desired effects, counties are divided into two types of boom and non-boom counties. The findings indicate that increasing natural gas production will lead to more employment and wage growth in boom counties than non-boom counties. Also, during the period of increasing production, the value of... 

Co-movement between inflation and nominal interest in response to an interest rate shock, dubbed neo-fisherianism, has been the subject of contentious debate since the advent of non-inflationary ZLB environment. We design an economic model rich with banking features to understand the economic responses to permanent and long-term interest rate shocks. We find that responses to a permanent positive interest rate shock depend on the monetary authorities’ speculation of the new long-term inflation rate, with the most probable outcome being a permanent increase in inflation. Responses to a long-term positive interest rate shock depict an increase and then decrease in inflation. We also discover... 

In this study, we aim to learn representations from microscopic cell images that effectively capture the features of drugs affecting the cells, allowing us to identify effective drugs for treating a disease. We employ two parallel learning paths using predictive and generative models. Specifically, we have achieved a predictive model on the RxRx19a dataset that, unlike previous models, is interpretable, optimized, and robust to dras- tic changes in drug properties. Additionally, we have developed the first generative model on this dataset, which not only generates high-quality images but also discovers a meaningful latent space. This latent space divides the representation into relevant...