Sharif Digital Repository

This research evaluates the fiscal regime of the National Iranian Oil Company (NIOC) and its impact on the company's performance. The main objective of the study is to examine the effect of the financial relationship between the government and NIOC over two time periods: before and after the 1979 revolution. Using a descriptive-analytical method, the research analyzes how changes in the fiscal regime and the government-NIOC relationship have influenced the company's production outputs. The results indicate that the fiscal regime and shifts in government policies have played a crucial role in NIOC’s performance, at times strengthening and at other times weakening its capabilities. The... 

Functionally graded materials (FGMs) are categorized in a branch of composite materials in which the local volume fraction of contributing phases are not fixed throughout the spatial domain, but vary gradually as a function of position. This spatial variation leads to the gradual variation of physical and mechanical properties inside the materials. It provides us the opportunity of designing multiple purpose materials by the variation of local volume fractions according to our goal. The optimal distribution of local volume fractions is a function of the spatial domain geometry and loading conditions, and in general situations, due to the complexity of the problem, it is not possible to... 

Because the structural stability is directly related with structural damage, it is considered one of the most important issues in the industry. One of the applied cases in the stability issue discuss about the stability of the beam under follower loads. Follower loads obtained from aerodynamic pressure, rocket’s thrust, dry friction of the rotating disk, drilling and etc. Because the follower loads are always perpendicular to the beam cross section, thus with changing the angle of their location, their directions are changed. Spatial dependence makes a non-conservative and dynamic problem. So these loads causes dynamic instability that say flutter. In this study, the stability of a... 

In this study, an analytical investigation of the hydrodynamic damping due to vertical baffles in circular cylindrical storage tanks is investigated. A lot of research about damping characteristics of different types of baffles has been done but because of specific applications of vertical baffles, studies are limited in this case. For analytical approach the average rate of energy dissipation is obtained with using the solution of Laplace’s equation by estimation the rate of the work done by baffles drag force to the oscillatory flow. The analytical solution validate by a series of experiments that conducted at the Langley Research Center of the National Aeronautics and Space... 

One way for businesses to grow and compete, in any age (especially the digital age), is to create a Brand Relevance through creating or finding, and then owning new categories or subcategories. In this way, instead of beating competitors; they become irrelevant by enticing customers to buy a new category or subcategory for which other alternative brands are not considered relevant. Firms traditionally rely on interviews and focus groups to identify these subcategories and customer needs. Nowadays, with the growth of social media, user-generated content (UGC) is also a good alternative source. However, Due to the large size of UGC and the non-informative or repetitive data it contains,... 

Double cantilever beam (DCB) specimens were prepared according to standard surface mount technology (SMT). The samples were stored inside an environmental chamber at two different relative humidity values (i.e. 40 or 100%) for either 2 or 4 hours. Then they were aged at 25ºC, 75ºC or 125℃ for the same time. Finally, after being cooled to room temperature, fracture tests were performed under mode-I loading conditions at a strain rate of 0.03 s-1 at room temperature. Storage time did not have a significant effect on the fracture behavior. The fracture load and energy of the solder joints decreased significantly when the temperature was increased from 25 to 75℃. By further increase in the... 

Long thin rectangular beams are used in many industrial engineering including railways, aerospace and etc. Beam subjected to moving mass is one of the classic problems in mechanics and vibrations of beams and have been studied by many researchers. In most of done works, the moving mass was assumed to be small compared to beam mass and only acceleration effect of mass was considered. Also in many of researches only bending of beams was studied. Moving mass imposes 2 type of force in the supporting beam, first one is weight and the other is due to motion of mass and contains lateral, coriolis and centrifugal acceleration effects. In addition, due to the particular geometry considered (narrow... 

In this thesis, effects of bending and torsional elasticity of a flapping wing on its average lift and input power are studied, using a semi-analytic method. Bending stiffness and torsional rigidity of wing spar, wing mass ratio and chordwise and spanwise center of gravity, also spar location are considered as variables for controlling elastic behavior of the wing.Governing integral equation is derived using Hamilton principle via modified quasi aerodynamic and linear Green-Lagrange strain tensor. Also an idealized flapping pattern is used to maximize average acceleration during each cycle. Next, integral equation is converted to a set of ordinary differential equations by means of Galerkin... 

The dry friction and its effect on the dynamics and vibrations of structures have always been one of the remarkable engineering issues. In the structures of engineering, dry friction mostly exists at the joints of structures and substrates and dry friction can lead to the nonlinearity and even chaos in the vibration of structures. There are different theories for the friction modeling and the most famous theory is the relation between the proportional ratio of the force of friction and perpendicular force to the surface. The main characteristic of friction as a damper force is the change of direction along with change in the direction of velocity. In the present study, at first, the nature... 

In the first description if we describe technology as a tool, Communication technologies or media should be consider as the most important element of today's technological world. This research is going to cover reconsidering and recreating the mean of media based on the Ideas of JacquesDerrida. In this regard, two major dichotomy is evident in the public understanding of media. meanwhile "media versus message" and on the other hand opposition between "media and audience". So deconstruction in the face of these binary oppositions, want to read out the notion that message is superior to media, and on the other hand to deconstruction of the hegemony of the media on the audience  

A new strategy for enhancing the efficiency of TiO2 dye sensitized solar cells (DSSCs) doped with Ni ions with different molar percentages (i.e., 0, 0.5, 1, 5 and 10 mol%) was reported. The samples were prepared by sol-gel route and characterized by means of XRD, DRS, UV-visible, FESEM and photovoltaic measurment techniques. It was found that Ni-doped TiO2 nanoparticles had a mixture of anatase, rutile and brookite crystal structures. Moreover, the band gap energy was decreased with increasing Ni molar ratio, The highest cell efficiency of 5.4% was achieved for 1mol% Ni-doped TiO2, being 42% greater than that of pure TiO2 nanoparticles