Machining precedence of 21/2D interacting features in a feature-based data model

, Article Journal of Intelligent Manufacturing ; Volume 22, Issue 2 , 2011 , Pages 145-161 ; 09565515 (ISSN) Mokhtar, A ; Xu, X ; Sharif University of Technology

2011

Abstract

In process planning, determining feature's machining precedence is an essential step. The task becomes more difficult if features interact with each other, in which case the feature precedence information may suggest multiple machining sequences of the features. This paper considers interacting features in a feature-based model for process planning tasks. For each feature, precedence information is generated considering both roughing and finishing operations. A rule-based system is developed and implemented based on the information about machining precedence of the interacting features. The STEP-NC data model is used as the underlying data model. This model is object-oriented and compliant...

Introducing a roadmap to implement the universal manufacturing platform using axiomatic design theory

, Article International Journal of Manufacturing Research ; Volume 5, Issue 2 , 2010 , Pages 252-269 ; 17500591 (ISSN) Mokhtar, A ; Houshmand, M ; Sharif University of Technology

2010

Abstract

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)

Integration of Design and Manufacturing Systems Using Neutral Data Structure

, Ph.D. Dissertation Sharif University of Technology Mokhtar, Alireza (Author) ; Hooshmand, Mahmoud (Supervisor)

Abstract

In competitive environment of quick market changes, developing an interoperable manufacturing system is a necessity. Process planning as a connection link between design and manufacturing, has never been able to integrate these up/down stream activities and in spite of employing computer systems, CAPP’s information has been managed in an isolated manner. To realize interoperability, the exchange of part and product data must be independent of their platforms. There are two basic approaches for this purpose: i) Utilizing interface and ii) Utilizing neutral formats. STEP (Standard for the Exchange of Product data) plays a significant role as a neutral data model to integrate design,...

Properties of the Cobalt Base Superalloys and the Effect of Remelting on Microstructure and Chemical and Physical Behavior

, M.Sc. Thesis Sharif University of Technology Mokhtar, Fatemeh (Author) ; Yoozbashizadeh, Hossein (Supervisor)

Abstract

Because of the importance and value of Superalloy, In this research has been treid to remelting scrap of gas turbine blades cobalt based Superalloy X-45, In order to restore it to the cycle of consumption. For this purpose, scraps were remelted under different conditions, for example changing the atmosphere, changing slag composition, changing type of the furnace for remelting and changing time of remelting process. Then in order to investigate effect of the above factors, microstructure were studied by optical microscope and Scanning Electron Microscopy (SEM) And also in order to investigate changings of element composition, chemical analysis were examined by atomic absorption analysis and...

Dealing with feature interactions for prismatic parts in STEP-NC

, Article Journal of Intelligent Manufacturing ; Volume 20, Issue 4 , 2009 , Pages 431-445 ; 09565515 (ISSN) Mokhtar, A ; Xu, X ; Lazcanotegui, I ; Sharif University of Technology

2009

Abstract

Determining the precedence of machining features is a critical issue in feature-based process planning. It becomes more complex when geometric interaction occurs between machining features. STEP-NC, the extension of STEP (ISO 10303) standard developed for CNC controllers, is a feature-based data model. It represents all the geometric and topological product data minus feature interactions. In this paper, machining precedence of interactive and non-interactive STEP-NC features is discussed. Local and global precedence of machining features are defined on the basis of geometric constraints, such as geometric interaction of features and feature approach face and technological constraint such as...

Model reduction techniques for unstable second order-form systems

, Article IEEJ Transactions on Electrical and Electronic Engineering ; Volume 16, Issue 3 , 2021 , Pages 445-454 ; 19314973 (ISSN) Ali, S ; Mohd Mokhtar, R ; Haider, S ; Bukhari, S. H. R ; Rasool, A ; Sharif University of Technology

John Wiley and Sons Inc 2021

Abstract

In the present work, multiple non existing model order reduction (MOR) techniques for unstable second-order form systems (SOSs) are proposed. For unstable SOSs, continuous-time algebraic Lyapunov equations get unsolvable that halt the reduction process. To avoid this problem, unstable SOS is first decomposed into stable and unstable portions and balanced truncation is applied to the stable part. The obtained reduced order model (ROM) for the stable portion is augmented with the unstable portion to obtain the overall reduced system. It is observed that the second-order structure in ROM for the first technique gets lost as well as augmented unstable dynamics degrade the ROM performance. To...

Model reduction techniques for unstable second order-form systems

, Article IEEJ Transactions on Electrical and Electronic Engineering ; Volume 16, Issue 3 , 2021 , Pages 445-454 ; 19314973 (ISSN) Ali, S ; Mohd-Mokhtar, R ; Haider, S ; Bukhari, S. H. R ; Rasool, A ; Sharif University of Technology

John Wiley and Sons Inc 2021

Abstract

In the present work, multiple non existing model order reduction (MOR) techniques for unstable second-order form systems (SOSs) are proposed. For unstable SOSs, continuous-time algebraic Lyapunov equations get unsolvable that halt the reduction process. To avoid this problem, unstable SOS is first decomposed into stable and unstable portions and balanced truncation is applied to the stable part. The obtained reduced order model (ROM) for the stable portion is augmented with the unstable portion to obtain the overall reduced system. It is observed that the second-order structure in ROM for the first technique gets lost as well as augmented unstable dynamics degrade the ROM performance. To...

Duty-cycle division multiplexing (DCDM)

, Article Optics and Laser Technology ; Volume 42, Issue 2 , 2010 , Pages 289-295 ; 00303992 (ISSN) Amouzad Mahdiraji, G ; Khazani Abdullah, M ; Malek Mohammadi, A ; Abas, A. F ; Mokhtar, M ; Zahedi, E ; Sharif University of Technology

2010

Abstract

A multiplexing technique, which is based on duty-cycle division, is proposed. The channel multiplexing and demultiplexing are performed electrically at the single user bit rate, which is very economic. In a three-user system (3×10 Gb/s), the simulation results show that the best receiver sensitivity value achieved is -30.1 dBm with an optical signal-to-noise ratio (OSNR) of 22.3 dB, while the chromatic dispersion tolerance ranges from 192 to 280 ps/nm. Migration from 30 to 120 Gb/s is achieved with the penalty of 6.4 and 5.2 dB in the receiver sensitivity and OSNR, respectively, for the worst user

Applying the Principles of Design for Manufacturing in Commercial Refrigerator and Freezer Industry

, M.Sc. Thesis Sharif University of Technology Ashkou, Mohammad Shahab (Author) ; Fatahi, Omid (Supervisor) ; Mokhtar, Alireza (Co-Advisor)

Abstract

Competitive world of industrial production need more speed and faster reaction for the customer needs. This should be carried out in low cost activities while satisfying what the consumers and customers require. Business of commercial refrigerators and freezers is a big industry targeting small to big customers. In this thesis a systematic method relying on reduction of cost, reworking and unexpected expenditures in product life is utilized. Stands for Design for Manufacturing, DFM is a series of principles and guideline simply to achieve a faultless design of a product so that the non-incurred costs of the product travel through its life cycle become minimized. Freezers and refrigerators...

A Novel Road Map to Develop a Feasible Framework for Collaboration Management in Tele-working Paradigm Based on Cloud Computing Theory

, M.Sc. Thesis Sharif University of Technology Edalat Javid, Negin (Author) ; Fattahi Valilai, Omid (Supervisor) ; Mokhtar, Alireza (Co-Advisor)

Abstract

Telework is an adaptable method for working which covers an extensive variety of work exercises in circulated associations comprised of people with robots and independent frameworks. From the levels of Nano and micro frameworks and gadgets the distance to the level of worldwide undertaking systems, beneficial work is reshaped by E-Work or Telework or Telecommute. The current work stresses on the part of learning administration as an empowering influence of E-Working standard. The four primary circles of information in e-Work related are: ‘‘e-Work”, ‘‘Integration , Coordination and Collaboration”, ‘‘Distributed Decision Support” and ‘‘Active Middleware”. Cloud computing can be distinguished...

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...

Investigation of Feed Type and Process Parameters in Ion Exchange Chromatography System for 15N Isotope Separation

, M.Sc. Thesis Sharif University of Technology Mokhtar Jozani, Fatemeh (Author) ; Outokesh, Mohammad (Supervisor) ; Karimisabet, Javad (Supervisor) ; Mansourzadeh, Fatemeh (Co-Supervisor) ; Dastbaz, Abolfazl (Co-Supervisor)

Abstract

The aim of this research is to find the optimal value of process parameters and type of feed in ion exchange chromatography system for nitrogen isotope separation and 15N stable isotope enrichment. First, by studying the articles and reviewing the previous works, the effective parameters on the ion exchange chromatography process were identified and the method of the process was determined. In the ion exchange chromatography process, various factors and parameters are effective, including the type of resin and its cross-linking percentage, the migration length of the ammonium band, the ambient temperature, the type of feed and elution solution, the concentration of feed and elution solution,...

Intelligent semi-active vibration control of eleven degrees of freedom suspension system using magnetorheological dampers

, Article Journal of Mechanical Science and Technology ; Volume 26, Issue 2 , 2012 , Pages 323-334 ; 1738494X (ISSN) Zareh, S. H ; Sarrafan, A ; Khayyat, A. A. A ; Zabihollah, A ; Sharif University of Technology

2012

Abstract

A novel intelligent semi-active control system for an eleven degrees of freedom passenger car's suspension system using magnetorheological (MR) damper with neuro-fuzzy (NF) control strategy to enhance desired suspension performance is proposed. In comparison with earlier studies, an improvement in problem modeling is made. The proposed method consists of two parts: a fuzzy control strategy to establish an efficient controller to improve ride comfort and road handling (RCH) and an inverse mapping model to estimate the force needed for a semi-active damper. The fuzzy logic rules are extracted based on Sugeno inference engine. The inverse mapping model is based on an artificial neural network...

Performance and exhaust emission characteristics of a spark ignition engine operated with gasoline and CNG blend

, Article Proceedings of the Spring Technical Conference of the ASME Internal Combustion Engine Division ; 2012 , Pages 179-187 ; 15296598 (ISSN) ; 9780791844663 (ISBN) Dashti, M ; Hamidi, A. A ; Mozafari, A. A ; Sharif University of Technology

2012

Abstract

Using CNG as an additive for gasoline is a proper choice due to higher octane number of CNG enriched gasoline with respect to that of gasoline. As a result, it is possible to use gasoline with lower octane number in the engine. This would also mean the increase of compression ratio in SI engines resulting in higher performance and lower gasoline consumption. Over the years, the use of simulation codes to model the thermodynamic cycle of an internal combustion engine have developed tools for more efficient engine designs and fuel combustion. In this study, a thermodynamic cycle simulation of a conventional four-stroke spark-ignition engine has been developed. The model is used to study the...

A comparative study of the performance of a SI engine fuelled by natural gas as alternative fuel by thermodynamic simulation

, Article 2009 ASME Internal Combustion Engine Division Fall Technical Conference, ICEF 2009, Lucerne, 27 September 2009 through 30 September 2009 ; 2009 , Pages 49-57 ; 9780791843635 (ISBN) Dashti, M ; Hamidi, A. A ; Mozafari, A. A ; Sharif University of Technology

American Society of Mechanical Engineers (ASME) 2009

Abstract

With the declining energy resources and increase of pollutant emissions, a great deal of efforts has been focused on the development of alternatives for fossil fuels. One of the promising alternative fuels to gasoline in the internal combustion engine is natural gas [1-5]. The application of natural gas in current internal combustion engines is realistic due to its many benefits. The higher thermal efficiency due to the higher octane value and lower exhaust emissions including CO2 as a result of the lower carbon to hydrogen ratio of the fuel are the two important feature of using CNG as an alternative fuel. It is well known that computer simulation codes are valuable economically as a cost...

Analytical and experimental analyses of nonlinear vibrations in a rotary inverted pendulum

, Article Nonlinear Dynamics ; Volume 107, Issue 3 , 2022 , Pages 1887-1902 ; 0924090X (ISSN) Dolatabad, M.R ; Pasharavesh, A ; Khayyat, A. A. A ; Sharif University of Technology

Springer Science and Business Media B.V 2022

Abstract

Gaining insight into possible vibratory responses of dynamical systems around their stable equilibria is an essential step, which must be taken before their design and application. The results of such a study can significantly help prevent instability in closed-loop stabilized systems by avoiding the excitation of the system in the neighborhood of its resonance. This paper investigates nonlinear oscillations of a rotary inverted pendulum (RIP) with a full-state feedback controller. Lagrange’s equations are employed to derive an accurate 2-DoF mathematical model, whose parameter values are extracted by both the measurement and 3D modeling of the real system components. Although the governing...

A suction-controlled ring device to measure the coefficient of lateral soil pressure in unsaturated soils

, Article Geotechnical Testing Journal ; Volume 44, Issue 1 , 2020 Pirjalili, A ; Garakani, A. A ; Golshani, A ; Mirzaii, A ; Sharif University of Technology

ASTM International 2020

Abstract

A suction-controlled ring device has been developed to continuously measure the coefficient of lateral soil pressure in deformable unsaturated soil samples from the at-rest to the active condition under application of increasing vertical pressure and controlled matric suction. The device incorporates a thin aluminum specimen ring equipped with horizontal strain gages for recording the lateral soil strains. In addition, a sensor recording water volume changes is utilized to continuously monitor the degree of saturation of the soil sample during tests. The matric suction within the soil texture is controlled using the axis translation technique. In order to verify the performance of the ring...

Gum tragacanth gels as a new supporting matrix for immobilization of whole-cell

, Article Iranian Journal of Chemistry and Chemical Engineering ; Volume 24, Issue 4 , 2005 , Pages 1-7 ; 10219986 (ISSN) Otady, M ; Vaziri, A ; Seifkordi, A. A ; Kheirolomoom, A ; Sharif University of Technology

2005

Abstract

We introduce a new smooth, non-toxic, biocompatible method for cross-linking of gum tragacanth (GT), a polysaccharide of natural origin, in order to serve as a new supporting matrix for immobilization systems. The modified gum is used as a matrix for the catalysis of the conversion of benzyl penicillin to 6-aminopenicillanic acid (6-APA) by means of Escherichia coli ATCC11105 with penicillin G acylase (PGA) activity. The results show that GT beads can not only serve as a proper matrix for immobilization, but show enhanced hydrolysis rate and stability compared to other immobilization systems used for this reaction. This signifies the potential of GT as a biocompatible matrix for...

True Class-E Design For Inductive Coupling Wireless Power Transfer Applications

, Article 30th International Conference on Electrical Engineering, ICEE 2022, 17 May 2022 through 19 May 2022 ; 2022 , Pages 864-868 ; 9781665480871 (ISBN) Haeri, A. A. R ; Safarian, A ; Fotowat Ahmady, A ; Sharif University of Technology

Institute of Electrical and Electronics Engineers Inc 2022

Abstract

The Class-E power amplifier has been widely studied and formulated in the literature. Although the majority of reported inductive coupling wireless power transfer (WPT) systems use a class-E power amplifier for driving the primary coil, still there is a lack of a comprehensive study on class-E circuit dedicated to WPT, providing a set of closed form design equations for proper class-E operation. This paper presents the required design equations needed to design a 'true' class-E circuit for WPT applications. Equations for the series-tuned secondary coil WPT system are presented, as well as two different design procedures for the parallel-tuned secondary coil. The derived equations have been...

Crashworthiness determination of side doors and B pillar of a vehicle subjected to pole side impact

, Article Applied Mechanics and Materials ; Vol. 663, issue , 2014 , p. 552-556 Lilehkoohi, A. H ; Faieza, A. A ; Sahari, B. B ; Nuraini, A. A ; Halali, M ; Sharif University of Technology

2014

Abstract

Pole Side Impact Tes is one out of three crash tests described by Euro NCAP standard for star rating of a vehicle and is required for assessing the Adult Occupant Protection. In this paper the goal is to determine the crashworthiness of side doors and B pillar in a Pole Side Impact Test based on Euro New Car Assessment Program (Euro-NCAP) using computer and simulation method. In this matter, a vehicle model has been prepared and meshed using Hypermesh and CATIA. The velocity of 29 km/h has been assigned to the vehicle which was on top of a cart while the pole has been assigned as a rigid static object based on Euro NCAP requirements specifically. Results show that different amounts of energy...