Sharif Digital Repository

In competitive environment of quick market changes, developing an interoperable manufacturing system is a necessity. To realise interoperability, the exchange of part and product data must be independent of their platforms. There are two basic approaches for this purpose: i utilising interfaces ii utilising neutral formats. Standard for the Exchange of Product data (STEP) plays a significant role as a neutral data model to integrate design, manufacturing and other activities in product life cycle. To implement a Universal Manufacturing Platform (UMP), a systematic roadmap is required. The current paper proposes such a roadmap using the methodology of Axiomatic Design (AD)  

Pavement performance models are key components of any pavement management system (PMS). These models are used in a network-level PMS to predict future performance of a pavement section and identify the maintenance and rehabilitation needs. They are also used to estimate the network conditions after the application of various maintenance and rehabilitation alternatives and to determine the relative cost effectiveness of each maintenance and rehabilitation alternative. Change in pavement surface roughness over time is one of the most important performance indicators in this regard. A model for changes in the international roughness index (IRI) over time was developed through artificial neural... 

This paper presents design and analysis of a cabledriven mechanism for a spherical laparoscopy surgical robot manufactured at the Research Center for Science and Technology in Medicine. The design is featured by two types of 'idler pulleys', which allow change of cables' plane of motion in spherical workspace. This robot suffers from back-lash and high friction due to the usage of motor and gear-box in each joint. In order to find a precise and optimal design, the paper studies various designs of cable robots, considering pulleys and cable arrangements, as well as pre-tensioning methods. Final scheme introduces two series of pulleys for each DOF, which transmits power from motors located on... 

Combined cycle power plants (CCPPs) play an important role in electricity production throughout the world. Their energy efficiency is relatively high and their production rates of greenhouse gases are considerably low. In a country like Iran with huge oil and gas resources, most CCPP's use natural gas as primary fuel and diesel as secondary fuel. In this study, effect of using diesel instead of natural gas for a selected power plant will be investigated in terms of exergy, economic and environmental impacts. The environmental evaluation is performed using life cycle assessment (LCA). In the second step, the operation of the plant will be optimized using exergy and economic objective... 

A framework to calculate a quantitative measure of seismic resilience using the Endurance Time (ET) method is introduced. ET method is a response-history based analysis procedure where structures are subjected to gradually intensifying dynamic excitations and their performance is assessed based on their response at different excitation levels, reducing the required computational effort. First, a prototype hospital building is optimally designed through three distinct design philosophies: prescriptive design code, performance based design criteria, and value based seismic design method. In value based design method, the design sections of structural elements are assumed as optimization... 

The objective of the present study is to depict an inclusive Construction Waste Management (CWM) plan looking at the total project life cycle. This holistic approach is called Integrated Construction Waste Management (ICWM). This research program has been conducted through several consecutive academic dissertations at Civil Engineering Department of SUT and was firstly aimed to identify waste sources throughout project life cycle. Concurrent research efforts were focused on project delivery methods evaluation, e.g. contract type effect on waste generation amount along with appropriate guidelines/incentives development that could promote ICMW. These studies were conducted via field... 

A new design methodology based on the total value of structures is introduced. This methodology, namely Value Based Design of structures (VBD), uses the advantages of Endurance Time (ET) method. While prescriptive and earlier generations of performance based design approaches commonly try to find structures with the least initial cost, a design approach to directly incorporate the concept of value in design procedure has been formulated here. Reduced computational effort in ET analysis provides the prerequisites to practical use of optimization algorithms in seismic design. A genetic algorithm is used with the objective of minimizing total cost of the building during its lifespan. ET method... 

Developing a computational model for studying tribological performance is essential for computing accurate life cycle of various materials. Caused by the existence of complicated and nonlinear interactions between material surfaces, exact modeling of wear behavior is very difficult. Artificial intelligence (AI) can be used in distinguishing similar patterns in experimental data and predictive modeling of a certain material’s wear behavior. In this paper, artificial neural networks (ANNs) approach, adaptive neural-based fuzzy inference system (ANFIS) technique, and fuzzy clustering method (FCM) are used to develop a simple, accurate, and applicable model for predicting the wear behavior of... 

Fixtures play a key role in locating workpieces to manufacture high quality products within many processes of the product lifecycle. Inaccuracies in workpiece location lead to errors in position and orientation of machined features on the workpiece, and strongly affect the assemblability and the final quality of the product. The accurate positioning of workpiece on a fixture is influenced by rigid body displacements and rotations of the workpiece. In this paper, a systematic approach is introduced to investigate the located workpiece position errors. A new mathematical formulation of fixture locators modeling is proposed to establish the relationship between the workpiece position error and... 

As a high proportion of the total generated electricity energy and the power system costs is due to the power losses in lines, allocating the loss and associated cost to the system loads and generating units is a substantial issue in deregulated power systems. The procedure to accomplish this cost allocation is designated as 'loss cost allocation' (LCA). So far, a number of LCA methods have been proposed for transmission networks. A few papers have compared different loss allocation methods, which are the methods which calculate the loss (and not necessarily the loss cost) allocated to the loads and generating units. However, this paper presents a comparative study of LCA methods. In this... 

The dynamic nature of today’s manufacturing industry, which is caused by the intense global competition and constant technological advancements, requires systems that are highly adaptive and responsive to demand fluctuations. Reconfigurable manufacturing systems (RMS) enable such responsiveness through their main characteristics. This paper addresses the problem of RMS configuration design, where the demand of a single product varies throughout its production life cycle, and the system configuration must change accordingly to satisfy the required demand with minimum cost. A two-phased method is developed to handle the primary system configuration design and the necessary system... 

Many industries are involved in production and distribution of perishable products. On one hand, due to the short life cycle of these products, there should be more precaution on the issues related to supply chain planning including material requirement planning, production, transportation, etc. compared to the ones in other industries. On the other hand, as there is a fierce competition among various companies, the need for coordination in such activities is imperative, where the use of an integrated approach is justifiable. One of these coordination problems is how to integrate important operational decisions including production scheduling and vehicle routing problem; the most important... 

This paper investigates the accumulation of technological capability in latecomer suppliers of complex capital goods by exploring the issue in an Iranian supplier of large hydro electricity generation systems. The findings suggest that, contrary to the conventional paths of catch-up in Asian and Latin American mass-producing electronics firms, and instead of starting from early stages of product lifecycle, the technological capabilities in this case were acquired through a non-linear movement within the stages of designing and installing complex capital goods in projects: starting from the middle stage (engineering and realisation of complex goods in projects), moving to the last stage... 

Aquifers are underground porous formations containing water. Confined aquifers are surrounded by impermeable layers on top and bottom, called cap rocks and bed rocks. A confined aquifer with a very low groundwater flow velocity was considered to meet the annual cooling and heating energy requirements of a residential building complex in Tehran, Iran. Three different alternatives of Aquifer Thermal Energy Storage (ATES) were employed to meet the heating/cooling demands of the buildings. These alternatives were using ATES for: Cooling alone, heating alone by coupling with at-plate solar collectors, and cooling and heating by coupling with a heat pump. For the economic evaluation of the... 

Despite the great promise of hybrid solar-wind-biomass energy systems to power future sustainable cities, complexities associated with their optimal planning and design limit their wide-scale implementation. This study provides a novel systematic framework to identify optimal hybrid renewable solutions for urban areas at neighborhood scales. In particular, we examine the role of economies of scale in the techno-economic feasibility and environmental performance of hybrid renewable systems. For demonstration, we assess the impact of the economics of scale (at the neighborhood scales of 1/500, 1/250, and 1/100 of the city's electrical load) on the life-cycle costs of optimal hybrid renewable... 

Significant energy subsidies are believed to be the main factor that has resulted in high energy intensities of Iranian industries. The Subsidy Reform Act of 2010 was directed at modifying energy consumption pattern and fostering energy efficiency enhancement. This study aims at analyzing the effect of energy subsidy reform on promoting energy efficiency in six energy intensive industries of Iran. In order to do so, the energy efficiency practices that have not been adopted after the implementation of the first phase of energy subsidy reform are investigated. Data analysis reveals that if financially interesting investments are determined as those with payback periods less than three years,... 

A variable air volume (VAV) air handling system can significantly reduce fan power under partial load conditions. The focus of this study is developing a modeling program to predict the potential energy saving by the secondary HVAC system strategies. Comprehensive steady-state models are established to describe the energy performance of different control strategies for secondary HVAC systems. With building loads, minimum fresh air flow rate, pressure losses, supply air temperature control, dampers control and coil characteristic as inputs, the objectives were to develop a simulation model to evaluate performance of an air handling system. The potential energy savings of constant air volume... 

The dynamic nature of today’s manufacturing industry, which is caused by the intense global competition and constant technological advancements, requires systems that are highly adaptive and responsive to demand fluctuations. Reconfigurable manufacturing systems (RMS) enable such responsiveness through their main characteristics. This paper addresses the problem of RMS configuration design, where the demand of a single product varies throughout its production life cycle, and the system configuration must change accordingly to satisfy the required demand with minimum cost. A two-phased method is developed to handle the primary system configuration design and the necessary system... 

In recent years, increasing attention has been paid to the use of renewable energy sources in building sector. The ground source heat pumps are a promising alternative for heating and cooling applications. Despite the high coefficients of performance and significant environmental benefits, their performance may deteriorate over the long-term operation if the annual ground loads are not well balanced. An appropriate solution is the use of hybrid ground source heat pump system through which some portion of the thermal loads can be offset by supplemental components. The aim of this study is to assess the feasibility of a solar-assisted ground source heat pump system for heating a detached house... 

Computational cost is one of the major obstacles for detailed risk analysis of structures. This paper puts forward a methodology for efficient probabilistic seismic loss assessment of structures using the Endurance Time (ET) analysis and the first-order reliability method (FORM). The ET analysis efficiently yields the structural responses for a continuous range of intensities through a single response-history analysis. Taking advantage of this property of ET, FORM is employed to estimate the annual rate of exceedance for the loss components. The proposed approach is an amalgamation of two analysis approaches, ET and FORM, that significantly lower the computational costs. This makes it...