Formation of ZrC-WC-W Composites Ceramics by DCP Method and Investigation of Their Physical Properties, Phase Composition and Microstructure

, M.Sc. Thesis Sharif University of Technology Davarpanah, Amin (Author) ; Faghihi Sani, Mohammad Ali (Supervisor) ; Mirhabibi, Ali Reza (Supervisor)

Abstract

Refractory metals (W,Re,Ta,Mo,Nb) and their alloys can exhibit exceptional properties at elevated temperatures. However, refectory metals tend to be relatively heavy and, in some cases, can be relatively difficult to form in complex shapes at low cost. Light composites of refractory metals with high-melting ceramics, which can be fabricated into dense, near net shapes at low temperatures, would be particularly attractive for advanced aerospace applications. In this project, WC powders have been pressed and shaped to cylindrical preforms. Secondly, these performs have been sintered slightly(presintered) into porous, rigid ones with about 50% open porosity. Finally, in order to reach dense...

High performance Dyneema® fiber laminate for impact resistance/macro structural composites

, Article Journal of Thermoplastic Composite Materials ; Volume 25, Issue 4 , 2012 , Pages 403-414 ; 08927057 (ISSN) Karbalaie, M ; Yazdanirad, M ; Mirhabibi, A ; Sharif University of Technology

2012

Abstract

UHMWPE composite materials are increasingly used in armors design due to their high strength-to-weight ratios and energy absorption capacities. In this study the effect of production parameters upon the terminal ballistic properties of UHMWPE composite were examined under different conditionings. The composite armor plate laminates were produced by hot pressing with three different pressing times from 10-30 minutes and the laminates conditioned at +115, +125, and +135°C. The molding temperature of SK66 fiber composite has the main direct effect on the ballistic absorption energy, so the relation of molding temperature with the adhesive bonding force between layers, the thickness of the...

Feedback control of the neuro-musculoskeletal system in a forward dynamics simulation of stair locomotion [electronic resource]

, Article Proc. of IMechE Part H: Journal of Engineering in Medicine ; 2009, Vol. 223, No. 6, pp. 663-675 Journal of NeuroEngineering and Rehabilitation ; Volume 11, Issue 1, 30 April 2014, Article number 78 Selk Ghafari, A. (Ali) ; Meghdari, Ali ; Vossough, Gholam Reza ; Sharif University of Technology

Abstract

The aim of this study is to employ feedback control loops to provide a stable forward dynamics simulation of human movement under repeated position constraint conditions in the environment, particularly during stair climbing. A ten-degrees-of-freedom skeletal model containing 18 Hill-type musculotendon actuators per leg was employed to simulate the model in the sagittal plane. The postural tracking and obstacle avoidance were provided by the proportional—integral—derivative controller according to the modulation of the time rate change of the joint kinematics. The stability of the model was maintained by controlling the velocity of the body's centre of mass according to the desired centre of...

Plastic Hinge Length and Drift Capacity of FRP Reinforced Concrete Columns under Seismic Loads

, M.Sc. Thesis Sharif University of Technology Mirhabibi, Maziar (Author) ; Kazemi, Mohammad Taghi (Supervisor)

Abstract

A brief overview of the proposed research, its aims, engineering relevance and applications; as well as expected achievements compared to the present state of the art:The plastic hinge length and ultimate drift calculations of frames are required in the performance based design of reinforce concrete structure. FRP-confinement increases the column’s shear resistance and ductility. FRP-confinement prevents concrete cover from spalling and increases the inelastic deformability of concrete in the potential plastic hinge region. GU et al. 2012 [24] studied the existing experimental results of confinement effects on the plastic hinge length. Mortezaei and Ronagh, 2012 [25], studied the plastic...

Synthesis and study of a new class of red pigments based on perovskite YAlO3 structure

, Article Ceramics International ; Volume 33, Issue 8 , December , 2007 , Pages 1427-1433 ; 02728842 (ISSN) Shirpour, M ; Faghihi Sani, M. A ; Mirhabibi, A ; Sharif University of Technology

2007

Abstract

A red pigment has been prepared by substituting chromium ions in aluminum ion sites in YAlO3 perovskite structure. In a first step, effect of various mineralizers on YAlO3 formation has been investigated, which resulted in decrease of formation temperature down to 1400 °C. In the next step, a red pigment corresponding to YAl1-yCryO3 (y = 0.05), has been prepared by heating a mixture containing Y2O3, Al2O3 and Cr2O3 at 1500 °C for 6 h. Later, effect of the doped chromium amount on the pigment redness (a*) has been studied. The highest redness has been obtained when y was 0.04(YAl1-yCryO3). Application of the prepared red pigment in low and high temperature glazes, demonstrated its high...

Developing an Applied Model for Energy Management in Dairy Production Industry

, M.Sc. Thesis Sharif University of Technology Bahmanpour khalesi, Ahmad Reza (Author) ; Mokhtar, Ali Reza (Supervisor) ; Miremadi, Ali Reza (Supervisor)

Abstract

Reviewing trends of energy consumption in the world reveals that sooner or later energy resources will be depleted. This concerning rate of consumption has brought about more greenhouse gases (GHG) emission influencing deleteriously on environment and climate. Human has continued energy consumption to maintain and improve the quality of his life through industrial production. Industry as a significant energy user owns considerable contribution to this consumption. Several attempts have been carried out to develop energy management systems in order to improve the energy efficiency of industrial sectors. Whilst they are comprehensive and could be applied to any sector, there is lack of...

An Experimental Study of the Effects of Sweep Wing on the Boundary Layer of 2D Wing

, M.Sc. Thesis Sharif University of Technology Tabrizian, Arshia (Author) ; Soltani, Mohammad Reza (Supervisor) ; Davari, Ali Reza (Co-Advisor)

Abstract

The behavior of boundary layer under the effect of the sweep angle is considered. The measurements were performed by a pitot tube rake. Three models with various sweep angels at angles of attack -2, 0 and 2 degree were tested. Both tip and root of all wings were closed by flat plates in order to prevent the flow to roll-up. However the flow field on the wing was still three-dimensional because of the sweep angle. The velocity on the wing has two components; longitudinal and lateral. The cross flow emerges due to the non-equilibrium of pressure and centrifugal forces. The velocity profiles showed that the magnitude of cross flow was stronger near the leading edge of the wing. The cross flow...

Gaining Competitive Advantage through Marketing Strategies in Container Terminal: A Case Study on Shahid Rajaee Port in Iran

, M.Sc. Thesis Sharif University of Technology Cheraghi, Hossein (Author) ; Miremadi, Ali Reza (Supervisor)

Abstract

The competitiveness of a port convinced shipping lines and shippers with a significant basis in selecting a port. Port authorities and port operators can make use of the competitive advantage as a parameter for counter measures by grasping the advantages and disadvantages of the ports and be a prime factor of opportunities and threats of the ports. Ports have a significant role in today’s networked business environment. They are being regarded as hubs that are part of various logistic systems. The very essence of a seaport is to link maritime networks and land network. These networks for the port are means of analyzing its competitiveness. A port overall competitiveness is determined by it’s...

Energy Management in Energy Harvesting Wireless Sensor Nodes

, M.Sc. Thesis Sharif University of Technology Rohbani, Nezam (Author) ; Ejlali, Ali Reza (Supervisor)

Abstract

Wireless Sensor Networks have become widespread because of their flexibility, applicability and ability to precept data with high accuracy. However, the most limiting factor in their usage is the amount of available energy in nodes since energy depletion in a node means that it is dead, therefore many efforts have been done for optimum energy management in Wireless Sensor Networks. In many cases, the key solution to prolong the network lifetime is load balancing. In this way, all the nodes will die (approximately) together and the lifetime of network will be maximized. Load balancing can be implemented in all layers from physical layer to application. It should be noted that it is not always...

Experimental Investigation of Mechanical Behavior of Structural Concrete with Combination of Waste Glass and Silica Fume

, M.Sc. Thesis Sharif University of Technology Faghihi, Kamyar (Author) ; Khaloo, Ali Reza (Supervisor)

Abstract

Concrete is the second most structural material in the world. So attention and promotion of the concrete mix design with respect to variable issues and requirements, is very important. On the other hand, these days environment and its pollution has become very popular discussion. Waste-glass which is produced by human products is one of the environmental pollutants. In this thesis it replaces some aggregate in concrete and it can reduce the level of this material in the world. Also we study effects of silica-fume as cement replacement and properties enhancer in our concrete mix design and see how it can ...

Strengthening RC Slabs under Various Loads and Boundary Conditions Using FRP Composites

, M.Sc. Thesis Sharif University of Technology Saber, Mostafa (Author) ; Khaloo, Ali Reza (Supervisor)

Abstract

In recent decades the use of FRP materials for strengthening structures has been developed extensively, thanks to their high strength, sufficient stiffness, high durablity, and ease of use. A great deal of research has been conducted on strengthening reinforced concrete beams and columns with FRP composites. By contrast, not many researches are performed on slabs, especially two-way slabs. In these few researches, the loading and boundary conditions are limited to simplest ones. Therefore, in this thesis, the focus of attention is on strengthening reinforced concrete slabs under various loads and boundary conditions using FRP composites.
In this thesis, first, FRP composites and their...

Optimal Batch Production for a Single Machine System with Rework

, M.Sc. Thesis Sharif University of Technology Haji, Babak (Author) ; Haji, Ali Reza (Supervisor)

Abstract

This research attempts to develop the optimal solution for an inventory problem consisting of a single machine which produces items some of which may be defective. We assume that no shortages are allowed and all defective items are to be reworked. Setup cost for rework and waiting time of defectives are considered. This research consists of two different parts. In the first part we consider two different policies where in the first policy in each cycle after the regular production the machine is setup for the rework of defectives of the same cycle. In the second policy several cycles constitute a period. All the defectives produced in the period are reworked in the last cycle of that period....

Improving the Reliability of Energy Harvesting Wireless Sensor Networks

, M.Sc. Thesis Sharif University of Technology Jalali, Fatemeh (Author) ; Ejlali , Ali Reza (Supervisor)

Abstract

Energy harvesters are used in today’s Wireless Sensor Networks (WSNs) to harvest the energy from the environment. One of the important advantages of the energy harvesting sensor networks over battery-operated sensor networks is that the use of the energy harvester prolongs the life time of the nodes, while a battery-operated node becomes useless once its energy runs out. Although an energy harvester can provide a supply source with a lifetime much greater than a battery, the amount of available energy for an energy harvesting system is a random variable and is not as predictable as the energy of a battery. This unpredictability may cause reliability problems. In order to solve the existing...

Response of Curved RC Shear Walls Under Cyclic Loading

, Ph.D. Dissertation Sharif University of Technology Abdoos, Hatef (Author) ; Khaloo, Ali Reza (Supervisor)

Abstract

Reinforced concrete (RC) shear walls with a curved cross-section are appealing structural elements to architects and engineers due to the aesthetic and structural advantages. Owing to the paucity of decent experimental research on curved RC shear walls (CRCSWs), the seismic response of these structural elements is essentially unknown. In that regard, this study includes research on a high-demanding type of structural element, which has found its application in North America, Europe, Asia, and to some extent in the Middle East with relatively no design specifications and laboratory research, structural analysis, and design methodology. Therefore, in order to provide an insight into the...

Selecting a Sustainable and Resilient Supplier in Cold Supply Chain Using Grey Multiple Criteria Decision Making Techniques

, M.Sc. Thesis Sharif University of Technology Farahmand, Mitra (Author) ; Hajji, Ali Reza (Supervisor)

Abstract

Supplier selection is a strategic decision that has a key impact on the success of the supply chain. Due to the nature of goods and storage conditions in the cold supply chain has a great impact on environmental pollution compared to other chains, and it also has the possibility of disrupting the chain due to the importance of temperature and time conditions. Currently, due to the spread of international pressures on the observance of environmental and social principles, the issue of choosing a sustainable supplier has been raised. Also, the expansion of supply chains has caused the challenges and risks faced by supply chains to expand and disrupt the chain, so the decision of supply chain...

Fabrication and Characterization of ZnO Composites Nanofibers by Electrospinning Method for Photocatalytic Application

, Ph.D. Dissertation Sharif University of Technology Samadi Amin, Morasae (Author) ; Moshfegh, Ali Reza (Supervisor) ; Pourjavadi, Ali (Co-Advisor)

Abstract

In this research we focus on study and fabrication of ZnO composite nanofibers by electrospinning method for photocatalytic application. The most important challenges in the field of photocatalyst are photocatalytic activity under the visible light and efficiency enhancement. ZnO is a wide band gap semiconductor and it is not active under the visible light. In Iran, we have more than 300 sunny days in a year. Therefore fabrication and application of photocatalytic material with activity under the sun light that contained 40% of visible light is so vital in our country. In the first part of this project, ZnO-CNT nanofibers were fabricated and carbon doped in the crystal lattice of the ZnO....

The Exploratory Study of Customer Satisfaction & Loyalty in Private Access Provider (PAP)Companies: ADSL Internet Case in Iran

, M.Sc. Thesis Sharif University of Technology Beheshtinejad, Ali (Author) ; Miremadi, Ali Reza (Supervisor)

Abstract

Internet and the market based on this new product and service has penetrated in all aspects of today’s modern life of human being. After invention of this market each day a new innovation revolutionized this market and industry. High speed internet based on ADSL technology was one of these innovations. The high-speed internet service has achieved a remarkable increase in penetration in recent years. In order to survive in this competitive market, companies should continue to improve their service performance. The high level of service performance is believed to be an effective way to improve customer satisfaction and loyalty. In recent years, the high-speed internet service, based on the...

Connected Covering on a Rectangulared Planar Subdivision

, M.Sc. Thesis Sharif University of Technology Khojamli, Halime (Author) ; Zarei, Ali Reza (Supervisor)

Abstract

This thesis is concerned with a fundamental problem in computational geometry. This problem inspects covering a space with a set of points provided that each point of the space is visible to at least one point from the selected subset. Applications of these problems are in the areas such as geographic information systems (GIS), robotics,computer graphics and the military.The investigated space is a planar rectangular region which is partitioned into smaller rectangles by connected edges. The objective of this study is to find an optimized corridor; i.e., a connected subset of edges which contains at least one point from each rectangle. For the minimum diameter corridor problem, an exact...

Low-power Design of Decimal Multipliers

, M.Sc. Thesis Sharif University of Technology Malekpour, Amin (Author) ; Ejlali, Ali Reza (Supervisor)

Abstract

Decimal multiplication is a frequent operation with inherent complexity in implementation. Commercial and financial applications require their data to be precise while binary number system cannot ensure precision. Existing research works on parallel decimal multipliers have mainly focused on latency and area as two major factors to be improved. However, energy/power consumption is another prominent issue in today’s digital systems. Hence, in this thesis we present a comparative study of parallel decimal multipliers, considering energy/power consumption (leakage and dynamic power consumption), latency and area. Furthermore, we present two novel techniques to reduce energy/power consumption of...

An Experimental Investigation of Transition Point Over a Quasi 2D Swept Wing by Using Hotfilm Sensor

, M.Sc. Thesis Sharif University of Technology Hassanzadeh, Maryam (Author) ; Soltani, Mohammad Reza (Supervisor) ; Davari, Ali Reza (Supervisor)

Abstract

In this study some experiments were performed to investigate the effect of sweep angle on the transition location of laminar flow to turbulent flow. Three half wing models were used, each having a different sweep angle but with the same aspect ratio in various angles of attack. Two flat plates were used at the ends of the swept wing models to prevent the flow from rolling up over the wing. By simulating flow over infinity swept wing by eliminating tip vertices, the effect of sweep angle on flow transition phenomenon was investigated.
The experiments included the study of transition flow via hot-film sensors, which were glued on the wing surface. We found that the small leading-edge...