Sharif Digital Repository

The main focus of this project is the fabrication of surface engineering scaffolds based on polyurethane and titanium dioxide. The research's aim is the creation of the synergistic properties of TiO2 and PU as a new strategy for engineering artificial autologous blood vessels. In the first section, PU-TiO2 nanocomposites were synthesized by co-insitu synthesis of nanoparticles and polymer. The nanocomposite films were prepared by solvent casting and thermally induced phase separation methods. Mechanical and biological properties of films were compared with pure PU film. In solvent casting method, the outcomes revealed that the rate of endothelialization of the nanocomposite scaffold after 7... 

Jacket type offshore platforms are classified as expensive and also strategic structures, and the cost of their maintanace is considerable. Therefore, any inspection and retrofit plans for life extension of the existing structures is economically and logically preferable rather than making decision for design and construction of new structures. The first stage of assessment plan is monitoring the performance of structure during critical loadings for which the structure is designed. One of the critical loads that should be considered in assessment of jacket structures is seismic loading. Due to dynamic nature of the applied loads in seismic assessment of jacket structures the accuracy of... 

Due to increasing competition, Flexible Manufacturing System (FMS) take more attention in the new world. This flexibility is generally considered to fall into two categories, which both contain numerous subcategories. The first category, machine flexibility, covers the system's ability to be changed to produce new product types, and ability to change the order of operations executed on a part. The second category is called routing flexibility. Due to high variation in parts and low production volume, setup times are important. In this research, Flexible Jobshop Scheduling Problem with Sequence Dependent Setup Time (SDST-FJSP), as an extension of classical Jobshop scheduling problem (JSP), is... 

In this project, a system designed for balancing a flexible rotor, without any need for shutting down the rotor. Then, functionality of this system, studied with experimental assessments. The method used in this plan, is classified into active online balancing methods of rotors which can change the mass distribution of the rotor, to improve the balancing condition, during operation. In order to reach this goal, a balancer plane is designed that by angular displacement of two nonconcentric masses, each driven with an electrical actuator, sets a desired unbalancy vector. Then, a rotor designed, which after mounting balancer plane, could be classified into the flexible rotors according to... 

In this research sequence-dependent flowshop and flexible flowshop group scheduling problems are investigated. Several upper and lower bounding methods are proposed for the research problems. Permutation flowshop sequence-dependent group scheduling problem with minimization of total completion time is considered. Since the problem is shown to be strongly NP-hard, a Memetic algorithm (MA) is proposed. A lower bounding method base on the Branch-and-Price algrithm is also proposed. A statistical comparison shows that both the proposed MA and the proposed lower bounding method have better performance than the other methods from the literature with an average 5.96% percentage gap. Flexible... 

The purpose of this research is to investigate the movement and diffusion of pollution transversely around a set of stems of flexible plants with different materials and to observe the effect of resonance on lateral dispersion. Two stem samples of polyurethane and nylon were used under different Reynolds numbers. Vertically uniform dye is injected into the flow, and the evolution of the dye plume along the flow is measured using image processing. By measuring the displacements of selected stems we study the effects of resonance on stem vibration and lateral dispersion. The experiments were also conducted for no-stem dispersion and the results were compared with those with plant samples. The... 

In this research, aeroelastic model of an elastic flapping wing has been derived in order to be integrated with the flight dynamic model. The model developed in this research well describes the coupled and nonlinear behavior of the passive torsional deformations of the wing during flapping motion. Based on this obtained equations, a precise propulsion model proper for flapping wing vehicles has been introduced. The effect of geometric and mechanical properties of the wing is being accounted. In order to validation of the analytical model several FMAVs as well as an instrumented test stand for online measurements of forces, flapping angle and power consumption have been designed and built... 

One of the challenges which increasing penetration of renewable energy sources with variable generation brings is the need for more flexibility in the power system. A promising way to overcome the challenge is to have local sources of the flexibility in distribution level. To this end, we present a new model for multi-stage distribution system expansion planning which jointly considers expanding the network assets and increasing the flexibility at local level by installing conventional dispatchable distributed generator units and energy storage systems. Demand response is also considered as another source of the flexibility which can be utilized by the system operator. Since deviating from... 

In this thesis, the equations of motion of a beam with tip mass on flying support, based on Euler-Bernoulli and Timoshenko beam theories is derived. To attempt for having accurate model in high rotational speeds, stretch variable is considered and employed in the equations of motion. For a planar and a spatial rotating beam, equations of motion are lineralized and simulated. Finite Element Method and Newmark direct integration scheme are employed for the analysis of the governing equations. To support the numerical results, an experimental setup is designed and based on which different tests are performed. A cantilever beam on a flying support free to vibrate in three dimensions is... 

Many spacecrafts and satellites have long flexible components, the most common ones are the satellites with flexible solar panels, which are used to provide the satellite energy. The governing equations of the satellite rigid motion along with the solar panels vibrations are the combination of the coupled partial and ordinary differential equations. Various reasons, such as the satellite maneuvers and the external disturbances, cause the vibration of panels. Due to the dependence between the governing equations of the satellite rigid motion and the flexible components vibrations, these vibrations affect the satellite rigid dynamics and the control aims; therefore, in addition to the... 

In recent decades, attention to renewable energy sources has been increased, and these resources will be an integral part of power systems in the future. Meeting the equilibrium point between power consumption and power generation at the power grid is of paramount importance. However, the equilibrium point is not solely dependent on the decisions of consumers and generation units and is influenced by other parameters as well. In this regard, penetration of renewable energies into the power system can affect this equilibrium point. These sources have random behavior, which will determine the future structure of the electricity grid. These sources can also change the shape of the network net... 

This study aimed to develop a green network design for a multi-echelon multi-product supply chain with a focus on bottleneck points as the means of enhancing unutilized capacities to maintain the optimal levels of flexibility. Two different models were developed to compare different approaches of flexible capacity planning by minimizing the total cost of facility establishment as well as their utilization and transportation cost. The proposed mixed-integer linear programming model was characterized by its novelty in taking bottleneck points into account to build a platform for flexible capacity planning required for responding to uncertainties such as fluctuations in demand and new product... 

By the use of flexible substrates like metal foils and meshes and plastic ones, fabrication of flexible dye sensitized solar cells are possible. Flexible dye sensitized solar cell, not only is utilized in portable, light electronic devices, but is also conductive to industrial roll to roll fabrication which enables the implementation of high throughput production lines and its associated potential reduction in manufacturing costs. This thesis has concentrated on fabrication of flexible dye sensitized solar cells by use of stainless steel mesh as substrate of photo-anode, because of its satisfying stability in electrolyte, flexibility, transparency and low cost. In this research, an efficient... 

Increasing variability and uncertainty in modern power systems may affect the systems’ reliable operation. This means higher needs for flexibility provision in power systems to meet the net load variability and uncertainty. Distributed energy resources (DERs) dispersed in distribution networks have noticeable flexibility capabilities which can provide required flexibility of distribution network while they can help the transmission network to acquire the flexibility requirements if appropriately aggregated and coordinated. This thesis presents a market-based hierarchical framework for exploiting DERs’ flexibility provision to meet intra-hourly variability and uncertainty of net loads in... 

The increasing variability of renewables and volatile chronological net-load in modern smart grids engenders significant operational risks of an uncertain sufficiency of flexible capacity. Assessing the operational flexibility of the grid with high penetration of renewable resources remains an issue of critical importance. Operational flexibility insufficiency may bring about two major problems: 1) there may exist no feasible solution for operation under uncertain conditions due to insufficient available flexibility capacity;2) even if the solution feasibility criterion is ensured, dispatch limitations of the flexible resources may force the system operating point to deviate from the optimal... 

In recent years, flexible electronics have started to attract a tremendeos amount of attention, partly on its remarkable growth in new technologies like IoT, wearable electronics, personal and health care devices. This emerging field offers many advantages compared to its traditional rigid counterparts, such as bendability, stretchablity, recyclability and biocompatibility. Inkjet printing is one of the most promising method for realizing flexible electronics due to its low-investment cost, fully additive nature, low material westage, relatively low temperature process and non-contact patterning.A printed circuit board (PCB), is undoubtedly a vital part of any electronics systems. So,... 

The present thesis investigates the micro-droplet dynamics in an inclined channel covered with flexible structures. For this purpose, the DPD (dissipative particle dynamics) method is used to study the behavior of particles present in the flow, including the droplet, the fluid around the droplet, and polymeric structures. This model leads to a more accurate representation of flow hydrodynamics and indicates the way for exploring and understanding complex fluid properties in real flows. The first part of the thesis deals with the dynamics of rising bubbles attached to a vertical wall under different wettability conditions. Even though bubbles rising freely in a liquid have extensively been... 

In a world where energy conservation is a critical topic, cooperative flexible manipulators will play an important role. Conventional robotic manipulators have been designed to have maximum stiffness to achieve both minimum vibration and good positioning accuracy of the end-effector, which causes more power consumption and reduced efficiency. Due to the high inertia of such arms, interaction with humans or sensitive environments is hazardous. On the other hand, Flexible Link Manipulators are designed to be lightweight, using lower energy and producing higher efficiency. Unfortunately, the link's flexibility increases vibrations and decreases the accuracy of the end-effector. Since, the... 

The competition between producers and the contracts issues between the producers and consumers of electrical energy in restructured power systems might cause on unwanted increase in power interchange beyond transmission lines capacity. If the power interchange is not well-managed, it would often cause overloads in specific path. This phenomenon is termed as lines congestion. The major goal of congestion management is to create a set of rules that ensure sufficient control over producers and consumers to maintain an acceptable level of power system security and reliability in the time of limitation of transmission network with maximizing economic market efficiency. As FACTS devices provide... 

Nowadays, variable generation and renewable energy resources are increasingly penetrating the energy systems to supply the users' demand at the distribution grid. Variable Energy Resources (VER) can provide energy at a lower cost, and they also guarantee cleaner energy. Still, the uncertainty and variability from these resources' output can affect the net-load of the system at each hour. Besides, the issue of energy balance has always been a challenge for the energy distribution networks. A comprehensive way to unravel this problem is to use flexible resources. One of the crucial issues in the flexibility debate is meeting this need by different energy resources. It is always an issue for...