Sharif Digital Repository

The aeroelastic behavior of wings made of functionally graded materials in supersonic flow is studied. For this purpose the flutter speed is calculated and in the next step the post flutter behavior is investigated. The structural model is based on the classical plate theory and material properties are assumed to be graded in the thickness direction according the power law distribution in terms of the volume fraction of material constituents. The linear piston theory which is modified to include thickness effects is used for supersonic aerodynamic modeling. The nonlinear structural model based on the Von-Karman strains is considered for prediction of the post-flutter behavior of the wing.... 

Facility location decisions play a prominent role in strategic planning of many firms, companies and governmental organizations. Since in many real-world facility location problems, the data are subject to uncertainty, in this thesis, we consider the P-center problem under uncertainty of demand nodes. Using Bertsimas and Sim approach, we modeled the problem as a linear optimization model. Furthermore, we develop a tabu search algorithm to solve the problem. Finally we designed some experiments to adjust the parameters of tabu search algorithm. We presented the numerical result accordingly  

Success in forecasting and analyzing sales for a given good or service can mean the difference between profit and loss for an accounting period and, ultimately, the success or failure of the business itself. Therefore reliable prediction of sales becomes a very important task. This thesis presents a novel sales forecasting approach by integration of Genetic Fuzzy Systems (GFS) and Data Clustering to construct a sales forecasting expert system. At first, we use stepwise regression analysis (SRA) to determine factors which have most influence on sales. At the next stage we divide our raw data into k clusters by means of K-means algorithm. Finally, all clusters will be fed into independent... 

Dynamic and vibration behavior of AFM microcantilever beam subject to the tip-sample interaction and/or contact is systematically investigated. An Euler-Bernoli microcantilever in 2D plane is considered with longitudinal and bending displacements. Inextensibility assumption and extended Hamilton’s principle is utilized to extract the single-variable integro partial equation of motion under: 1) tip-nanoparticle interactions, 2) tip-surface interactions in non-contact mode and 3) tip-surface interactions and contacts in intermittent-contact mode. Galerkin’s first mode approximation is then used to discretize the derived equations; and multiple time scales method is adopted to analyze the... 

In this research, an anistropic thin-walled beam composite is used to consider the effects of fiber orientation and lay-up configuration on the aeroelastic stability and response of an aircraft wing. The circum ferentially asymmetric stiffness (CAS) model consists of a group of non-classical effects; such as transverse shear, material anisotropic, warping inhibition, etc. The aerodynamic load has been modeled based on the strip theory and compressible unsteady flow in the finite- state form. In addition, to form the mass, stiffness and damping matrices of non-conservative aeroelastic systems the extended Galerkin’s method (EGM) and the method of separation of variables has been used. After... 

This thesis presents the results of an experimental and analytical study on the application of the strapping technique for seismic retrofit of reinforced concrete columns. In this technique, the columns are externally confined by post-tensioned metal strips. In the first phase of the experiments, the compressive stress-strain behavior of strapped cylindrical and prismatic specimens was studied. Effects of several parameters were studied including shape and size of specimens, strength of plain concrete, mechanical characteristics of confining strips and the level of pre-tensioning of the strips. The second phase of the tests included studying the lateral performance of strapped RC columns.... 

In order to reduce structural and nonstructural damages and associated financial losses during intense seismic events such as Bam earthquake, seismic retrofitting of existing structures should be considered as a special issue. In this regard, for quantifying the seismic performance of structures a guideline termed “instruction for seismic rehabilitation of existing building No.360” is issued which is mainly borrowed from performance-based assessment procedures FEMA 356. In contrast to conventional seismic design methods which are based on controlling stress ratio for different load combinations, in performance-based earthquake engineering methodology, the displacement control of structural... 

In the last decade, Intrusion Detection Systems has attracted attention due to their importance in network security, but still they've shortcomings. Generating a lot of low level alerts is the main problem. Many of these alerts are actually false positives. One suggested solution is Alert Correlation Analysis. Because of false positives alert correlation techniques are not able to build accurate scenarios, but the accuracy of alerts can be verified with the aid of the information logged in the host systems. In this dissertation after surveying the current alert correlation techniques, a model will be introduced to effectively verify the generated alerts and to apply correlation techniques to... 

Considering the role of fluid storage tanks within or after an earthquake and the irreparable damages from their destruction that arise from the nature of the fluids of flammable or toxic nature stored in those tanks, it is very important to ensure stability and durability of the tanks when an earthquake is occurring. One of the most important damages to storage tanks within the past earthquakes has been lack of stability of their walls taking place in the form of elephant buckling. A certain storage tank was subject to a case study in this research and the tank's body, foundation, anchorages, the tread between the fluid and tank's body and between the bottom sheet and foundation were... 

This research proposes a novel hybrid method for stock price index forecasting relying on technical analysis, the fundamental analysis of capital market, neural networks technology, and fuzzy logic. The new method shows a good performance comparing complicated and time-consuming forecasting methods. Several factors influence stock price; for example, an important one is the previous trend of stock price. Fortunately, by developing technical analysis and introducing the various indices of this method the maximum use of historical data is made in order to forecast future prices. Another kind of factors is macro-economic variables that their influence on the long-term trends of the stock... 

Masonry buildings are wide spread in Iran and some other countries . These buildings are highly vulnerable to seismic excitations if not constructed in accordance with engineering fundamentals . Thus it is necessary to retrofit these structures to flee from humanitarian and economical damages inflicted by earthquakes. One of the critical vulnerabilities of masonry buildings is due to transverse instability of it’s infills . Therefore to study out of plane behavior of these elements , an infilled frame is modeled and analyzed with ABAQUS , the results of which is in good congruence with the experimental one . In this model , stress distribution due to one way arching action in the confined... 

In this thesis a 2-3PRS hybrid mechanism is presented. This manipulator is consisted of two serially connected parallel 3PRS mechanisms, each mechanism has three degrees of freedom, so that the overall degrees of freedom of the manipulator are six. The relations for position, velocity and acceleration of the mechanism in both forward and inverese kinematics are derived and then singular points are determined. After that, the inverse dynamic equations for one of the 3PRS mechanisms are derived through the Newton-Euler and aslo Lagrange approach and the results are verified. Then the derived Newton-Euler equations are implemented for inverse and forward dynamics of the hybrid manipulator. The... 

Web service plays an important role in software development. Since Web service can be used in small scale and large scale environments, many different entities may participate in each interaction. Regarding situation, a lot of information is available around these entities. This kind of information is called context. In some cases, context information is used to provide outputs which are called context-aware systems.
The main challenging issue in producing a context-aware system is context modeling and sharing. Semantic Web and its ontology languages are the most promising solution to context modeling. In pervasive computing many ontologies are proposed for this purpose, but little... 

Protein multiple sequence alignment is one of important problems in biology which no polynomial time algorithms is known for it yet. Due to importance of this problem, several methods have been developed to find an approximate solution for it. Approximation algorithms, Evolutionary algorithms and Probabilistic methods are some of these methods. According to evolutionary nature of this problem, evolutionary algorithms and specifically genetic algorithms can be a potential good solution method for this problem. In this project we have a survey on using genetic algorithms for this problem and after mentioning benefits and draw backs of existing methods, we develop a method for improving one of... 

Today many applications produce data stream that grow continuously over time. Classification is an important task in mining this data. One of the major challenges in classification of data streams is that the underlying concept of data may change over time; this needs updating the classification model. Many of traditional classification algorithms are adapted for classifying data streams. Evolutionary algorithms are stochastic methods that have been successfully applied to a wide range of optimization problems. Harmony search is a new evolutionary algorithm that convergence to global optimum and can be applied to discrete and continuous data. The evolutionary nature of classifying data... 

Planning safe rendezvous and docking trajectories between two spacecrafts has a high importance in the space applications. In order to make two spacecrafts moving in different orbits closer, two stages must be completed simultaneously: First the implementation of rendezvous maneuver which deals with the generation of control/guidance commands leading to trajectories that lead the chaser towards the target. Second the docking maneuver incorporation which makes the two spacecrafts closer with the relative zero attitude. Various approaches have been dealt with till now using the analytical and numerical approaches generally considering rendezvous, not the docking maneuver. These approaches... 

In this project Deployment of multi-agent systems was studied. Maximum coverage over a point or curve or area is desired in deployment of multi-agent systems. A facility location optimization function was derived from geometrical concepts such as voronoi, n- geometric median and fermat-weber problem by optimization of which the deployment of multi-agent systems is performed. First, it is assumed that dynamic of agents is first order and second order .Next, it is assumed that agents are in a fluid. In all situations a suitable control algorithm was derived to optimize the facility location function to perform deployment. Next, another facility location function was derived by optimization... 

Vibrational modeling of a gas turbine considering simultaneous faults is considered. Faults including: unbalance, misalignment, and rotor crack are selected to be modeled. Oil film forces of hydrodynamic bearings are chosen as the supports of the rotor. Modeling starts with choosing an appropriate finite element model for the rotor which includes the effects of shear deflection, rotary inertia, gyroscopic moment, and rotor cross section variation. Modeling of unbalance is in fact a part of rotor finite element modeling. The forces that origniate form misalignment are computed using the static relations of a rigid coupling. Modeling of bearing faults along with bearing forces is performed... 

Sensor Observation Service (SOS) which is defined by Open Geospatial Consortium (OGC) Sensor Web Enablement group is a Web service specification in order to standardize the way sensors and sensor data are discovered and accessed on the Sensor Web. Multiple instances of this service can be implemented around the world, providing huge amount of data every moment. Each of these services operates in specific domain of knowledge (thematic), spatial and temporal dimensions. One way to reveal the underlying data over all of them is to provide an architecture for data integration to allow the user to query sensor data without the knowledge of the infrastructure components. In this research, a novel... 

The application of manipulators is becoming more and more popular in objects handling especially when it is desired to have access to remote areas in destructive or hazardous taskspaces. For this purpose, a hand-like mechanism must be designed to be used as an end-effector, which can grasp objects. In this paper a cable driven grasping mechanism has been presented. In the proposed mechanism each finger consists of three phalanxes which are actuated by a single motor. Also, locking and unlocking constraints are used in the mechanism in order to generate an anthropomorphic motion, in which, the order of reaching phalanxes to the object is sequential, in such a way that each phalanx starts...