Sharif Digital Repository

A lot of projects in real life are subject to some kinds of nonrenewable resources that are not exactly similar to the type defined in the project scheduling literature. The difference stems from the fact that, in those projects, contrary to the common assumption in the project scheduling literature, nonrenewable resources are not available in full amount at the beginning of the project, but they are procured along the project horizon. In this paper, we study this different type of nonrenewable resources. To that end, we extend the resource constrained project scheduling problem (RCPSP) by this resource type (RCPSP-NR) and customize four basic branch and bound algorithms of RCPSP for it,... 

During recent years centrifugal-based microfluidic devices known as Lab-on-a-CD have attracted a lot of attentions. Applications of these CD-based platforms are ubiquitous in numerous biological analyses and chemical syntheses. Mixing of different species in microscale is one of the essential operations in biochemical applications where this seemingly simple task remains a major obstruction. Application of centrifugal force, however, may significantly improve the flow agitation and mixing, especially when it is combined with the Coriolis force which acts perpendicular to centrifugal force. In this study, mixing process in minichambers located on a rotating platform under a periodic... 

During recent years centrifugal-based microfluidic devices known as Lab-on-a-CD have attracted a lot of attentions. Applications of these CD-based platforms are ubiquitous in numerous biological analyses and chemical syntheses. Mixing of different species in microscale is one of the essential operations in biochemical applications where this seemingly simple task remains a major obstruction. Application of centrifugal force, however, may significantly improve the flow agitation and mixing, especially when it is combined with the Coriolis force which acts perpendicular to centrifugal force. In this study, mixing process in minichambers located on a rotating platform under a periodic... 

This research studies multi-objective master production schedule (MPS) and advanced order commitment (AOC) in two-stage supply chains. Simulation-based experimental analysis evaluates the impact of environmental and MPS design factors on schedule cost and instability. The results provide insight into multi-objective MPS design considerations through rolling schedule policies. The study reveals that the manufacturers production smoothness utility coefficient and its interaction with other experimental factors considerably impact on the systems performance. In addition, it introduces a simulation framework with embedded mixed integer programming models that could be used as a framework for... 

A brass vortex tube with changeable parts is used to obtain the optimum nozzle intake numbers and diameter. The effects of inlet pressure and CF (cold fraction) are also investigated. Results illustrate that increasing the number of nozzles causes a temperature drop and the optimum nozzle diameter corresponds to quarter of vortex tube diameter. The distance between cold end orifice and nozzle intakes is investigated in this work and it is found that for a better performance, this distance should be decreased. A series of experiments conducted to investigate the CF effect on VT performance and an optimum amount for this parameter is found. A two-dimensional computational fluid dynamics... 

This paper investigates the free vibrations of a shell made of n cone segments joined together. The governing equations of the conical shell were obtained by applying the Sanders shell theory and the Hamilton principle. Then, these governing equations are solved by using the power series method and considering a displacement field which is harmonic function about the time and the circumferential coordinate. Using the boundary conditions of the two ends of the shell and the continuity conditions at the interface section of shell segments, and solving the eigenvalue problem, the natural frequencies and the mode shapes are obtained. Very good agreements exist between the analytical results of... 

Supplier selection is a decision-making process to identify and evaluate suppliers for making contracts. Here, we use interval type-2 fuzzy values to show the decision makers' preferences and also introduce a new formula to compute the distance between two interval type-2 fuzzy sets. The performance of the proposed distance formula in comparison with the normalized Hamming, normalized Hamming based on the Hausdorff metric, normalized Euclidean and the signed distances is evaluated. The results show that the signed distance has the same trend as our method, but the other three methods are not appropriate for interval type-2 fuzzy sets. Using this approach, we propose a hierarchical... 

In the present study, the experimental analysis of a second-throat exhaust diffuser (STED) performance has been conducted for the high altitude test of a parabolic bell-type nozzle. The diffuser starting performance has been explored considering two different approaches, namely the gradual and instantaneous increase of the nozzle chamber pressure. Also, the influence of pre-evacuating the internal regions of the system on the diffuser starting performance has been studied. Numerical simulations have been carried out to have more physical insight into some test results. It is demonstrated that the non-dimensional hysteresis range in STED starting performance with a bell-type nozzle is up to 4... 

In this article, we present a novel framework based on incoherent holography (IH) and optical phase conjugation (OPC) principle for imaging through scattering media. While many different methods have recently addressed the issue of focusing light inside scattering media or through-scatterer imaging, the majority of them suffer from severe drawbacks, such as demanding for a high-intensity and narrow-bandwidth laser illumination and an extremely stable optical setup in digital holography as the normal disadvantages of interferometry. On the contrary, our proposed framework relaxes the need for interferometry by getting advantage of its IH-based structure. Our newly presented approach for... 

The strain-induced martensitic transformation greatly affects the plastic behavior of the metastable austenitic stainless steels. The martensitic transformation continuously changes the initially homogeneous material into a strongly heterogeneous bi-phase one. In addition to the hardening behavior, this phenomenon would influence the damage growth and load-carrying capacity of the material during the plastic deformation. In this study, plastic behavior of the material AISI 304 including the hardening and damage growth, has been examined at low temperature; where a high rate of martensitic transformation affects the microstructure strongly. Experimental analysis and microscopic observations... 

An experimental investigation of the shock-buffet phenomenon subject to unsteady pitching supercritical airfoil around its quarter chord has been conducted in a transonic wind tunnel. The model was equipped with pressure taps connected to the fast response pressure-transducers. Measurements were conducted at different free-stream Mach number from 0.61 to 0.76. The principle goal of this investigation was to experimentally discuss the shock-buffet criterion over a SC(2)-0410 supercritical pitching related to the hysteresis loops of total drag and trailing edge pressure, the behaviour of the shock wave foot location, the pressure distribution over the upper surface, and by implementing the... 

Theoretical and experimental analysis of performance of a solar desalination pond as a second stage of proposed zero discharge desalination processes is considered in this work. Major purpose of this proposed process is producing salt and potable water. Experiments are conducted for brackish wastewater with different salinity content. The relation between temperature variations of brackish water, glass, and base of solar desalination pond with condensation rate are discussed. Results indicate when brackish water temperature is increasing; the average daily production of solar desalination pond is increased considerably. Results of the mathematical modeling show good agreement with... 

In this paper, Plate Frame Interaction (PFI) developed by other researches for modeling Steel Plate Shear Wall (SPSW) is applied for designing a half-scale, single bay and one story SPSW. After designing of SPSW, one specimen is constructed accordingly. In order to determine the mechanical properties of steel, coupon test is performed; and then again theoretical relations based on PFI is re-checked. In this study, gravity loads are neglected and only seismic resistance of SPSW is considered. With cyclic lateral loading as quasi-static load, according to Acceptance Criteria for Cyclic Racking Shear Tests For Metal-Sheathed Shear Walls with Steel Framing (AC154) and obtaining its hysteretic... 

This work concerns with experimental and analytical investigation of role of ultrasonic wave radiation in relative permeability of both wetting and non-wetting phases in a free gravity drainage process in porous media under the influence of ultrasonic wave. Glass beads ranged from 70 to 100 mesh sizes were packed and used in the tests. The working fluids consist of distilled water, kerosene and Doroud and Paidar crude oils as wetting and air as non-wetting phase. The measured oil recovery data along with Hagoort (1984) backward methodology were used to determine and to compare the relative permeability of wetting phases in presence and absence of ultrasonic radiation. In addition, the... 

In this paper, the effect of different parameters of power plants, such as height above sea level, performance, ambient temperature, fuel type on emissions in Iran's power plants is investigated. Based on that, a general strategy for selecting the type of power plant, fuel that fit with the geographical situation in the Middle East is presented. Results taken from this scientific study shows that using natural gas to generate power in the region should be a priority. As well as expected, the value of various emission factors decrease by increasing power produce. Also the emission factors of combined cycle power plants are the lowest as compared to other types of power plants  

An attempt was made to examine thermal effects as well as fade and wear characteristics of rubber-based friction materials (RBFMs). A series of RBFMs with and without fiber reinforcements were prepared. The fiber reinforcements used were carbon fiber, cellulose fiber and aramid pulp. A semi-empirical model describing the correlation of coefficient of friction (COF) and temperature was presented. The effectiveness of the model was evaluated using the experimental data. The results revealed that the model parameters for a given composite show a significant change above a critical sliding velocity, i.e. 300 rpm. This behavior was speculated to be due to the transition of rubbery state of the... 

The perspectives of utilization of a screen mesh heat pipe (HP) for low to medium operating temperature applications are studied in this study. A two-dimensional mathematical model for heat and mass transfer of HPs is presented to define its performances under steady state operations. The model couples heat conduction in the wall with both liquid flow in the wick and vapor flow in the core. Experimental analysis is developed to evaluate the influence of operating parameters (the orientation and the cooling temperature) as well as the evaporator section length on the performance of the HP. Furthermore, a modeling approach to optimize the HP performance from a thermal point of view is... 

This paper addresses a low complexity and high efficient cooling system applicable on photovoltaic (PV) system leading to enhance electrical efficiency and provide preheated water. The developed system consists of a photovoltaic panel, a cooling water system establishing a uniform surface temperature, and a solar water heater. According to the proposed system characteristics, the setup is constructed based on a single mono-crystalline solar panel to absorb more solar radiation intensity and generate more electrical energy per area in compare to a poly-crystalline panel. The preheated water produced by absorbed heat from the photovoltaic is conducted to a solar water heater to satisfy... 

The characteristics of a cavitation water tunnel test setup and the experiments of cavitation around a circular cylinder with free stream turbulence are presented in this paper. The Reynolds number of flow is limited in the range of 1.26 × 105 to 3 × 105 and the far upstream flow has free turbulence. Drag force, back pressure, location of cavitation inception, length of cavity and appearance of cavitation are measured or observed and their results are presented here. It was found that the cavitation effects on the boundary layer and separation of flow over the cylinder and drag force become minimum at the cavitation number of 1.94. The cavitation inception occurs in the sub-layer and at an... 

Numerical analysis of the nanofluid flow characteristics of perforated conical rings in a heat exchanger tube has been investigated under constant wall temperature condition. The pitch ratio of the perforated conical rings is 4 and the number of holes is varied from 0 (typical conical ring) to 10. The flow regime is fully turbulent with the Reynolds number is varied from 5000 to 14,000 and Cu-water nanofluid 0<ϕ<1.5% is selected as the working fluid. The main novelty of this paper is to perform a 3D simulation of this problem because some previous studies using similar geometry were restricted to experimental analysis. The Reynolds averaged Navier Stokes (RANS) equations are solved with the...