Search for: two-stage
Total 97 records
The effect of addition of Tiron as a surfactant on the microstructure of chemically deposited zinc oxide, Article Materials Science and Engineering B: Solid-State Materials for Advanced Technology ; Volume 128, Issue 1-3 , 2006 , Pages 53-57 ; 09215107 (ISSN) ; Vaezi, M. R ; Sharif University of Technology
The effect of one of the surfactants such as Tiron, a compound based on the benzene molecule, on the morphology and chemical composition of zinc oxide deposits, produced from a zinc complex solution using two-stage chemical deposition (TSCD) technique, has been investigated. TSCD technique is a novel and simple chemical route for the deposition of ZnO film from aqueous solution. Zinc oxide films deposited on high purity alumina (HPA) as a substrate. The results show that the addition of Tiron changes the surface morphology and causes to form the fine-grained structure. With a dense and nodular-shape appearance, the film produced from the precursor of zinc complex-containing Tiron, is...
Article Amirkabir (Journal of Science and Technology) ; Volume 14, Issue 56 C , 2003 , Pages 1185-1198 ; 10150951 (ISSN) ; Asghari, G ; Sharif University of Technology
This study investigates validity of continuity assumption of error terms underlying multiple linear regression approach of trip generation models for infrequent trips. Since not many household members make daily trips for purposes like shopping or personal business, estimation of such trips with their discrete and non- negative nature and still close to zero averages, using conventional multiple linear regression, needs to be investigated. This study employs a two-stage trip generation model; the probability of making/not making trip is modeled first by binary probit, then, number of trips for those who have already made trips are estimated by the weighted least square method. The results...
Article IEEE Transactions on Very Large Scale Integration (VLSI) Systems ; Volume 26, Issue 10 , 2018 , Pages 2038-2049 ; 10638210 (ISSN) ; Sharifkhani, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc 2018
A low-power comparator is presented. pMOS transistors are used at the input of the preamplifier of the comparator as well as the latch stage. Both stages are controlled by a special local clock generator. At the evaluation phase, the latch is activated with a delay to achieve enough preamplification gain and avoid excess power consumption. Meanwhile, small cross-coupled transistors increase the preamplifier gain and decrease the input common mode of the latch to strongly turn on the pMOS transistors (at the latch input) and reduce the delay. Unlike the conventional comparator, the proposed structure let us set the optimum delay for preamplification and avoid excess power consumption. The...
M.Sc. Thesis Sharif University of Technology ; Hajji, Rasul
In the present research a two stage supply chain is considered. In its first echelon, there is a producer that produces both perfect and defective items. Defective items are reworked by producer and no defective item is produced during the reworking process. There is a buyer in second echelon of the supply chain that faces constant demand and orders fixed batches in fixed periods to the producer. So in each complete cycle of production, multiple orders are received from buyer. Two different policies for reworking are investigated in this research. In the first policy, reworking is done in the same cycle that producing is conducted but in the second one all defective items that are produced...
M.Sc. Thesis Sharif University of Technology ; Kianfar, Farhad
In this thesis we investigated a two level seller-buyer supply chain by game theoretical approach. We formulated interaction between seller and buyer as stackelberg game. In seller-stackelberg game , seller role as leader and buyer as follower. likewise in buyer-stackelberg buyer is leader and seller is follower. In our model the demand is an equation in which the dependent variable is a linear function of three independent variables and a disturbance term. The three independent value in demand function are marketing cost , wholesale price , retailing price. The disturbance term in demand function has normal distribution by constant variance and zero expected value. Sale amount considered as...
M.Sc. Thesis Sharif University of Technology ; Keshavarz Haddad, Gholamreza
Increases in food prices after the energy prices reform in Iran 2010, have raised concerns about reductions in households’ wellbeing and food security. Particularly for the families in the lower income quintiles who spend large fraction of their earnings on food and sheltering. This research intends to evaluate the welfare consequences of the increases in commodity prices on Iranian urban households by making use of a two-stage Quadratic Almost Ideal Demand System (QUAIDS), censored data and Compensation criterion. The demand system is estimated based on cross-section data which are taken from households’ expenditures and income surveys for years 2010 and 2011. Our results show that the own...
plasma Electrolytic Oxidation of AZ31 in Silicate and Phosphate Electrolyte and Study of Corrosion Behavior, M.Sc. Thesis Sharif University of Technology ; Ghorbani, Mohammad
In recent years, magnesium and its alloys have been considered as biodegradable implants, but they corrode in the body before natural process of damaged organs recovery is completed. In this investigation PEO operation was used for corrosion control and effect of different parameter such as number of operation steps, electrolyte type, time and operation voltage on coating properties was studied. Scanning electron microscopy was used for investigating of morphology of coats and to determine chemical composition and phase of coats EDS analysis and X-ray diffraction were used. The corrosion resistance of samples were evaluated by potentiodynamic polarization and electrochemical impedance (EIS)...
M.Sc. Thesis Sharif University of Technology ; Fotuhi-Firuzabad, Mahmoud
Power distribution systems have been traditionally operated as passive networks which consume electric power supplied by the transmission grid. Increasing utilization of wind energy in distribution systems, notably wind energy, is changing the way distribution sys-tems are operated. The distribution system operators (DSO) would operate the available wind power for reducing the power purchased from the wholesale market. However, high penetration of wind energy in distribution systems would require advanced operation mod-els and additional flexibility in system to offset the variability and uncertainty associated with wind energy. In addition, wind availability often does not positively...
M.Sc. Thesis Sharif University of Technology ; Arghavani Hadi, Jamal
Powder metallurgy is one of the most important and most usable methods in industries. Nowadays, many of the specimens are made this way. In this method, after powder compaction stage, because of sintering in high temperature, crystallographical structure of the material changes. This change results in poorer strength than initial powde. In order to avoid change and decrease in powder strength, shock consolidation is used. In this research, because of complication of this phenomenon and final quality of the specimen, shock consolidation of metal powders is investigated and analysed. This phenomenon is modeled, simulated, analysed and optimized mathematically.Various methods are used to create...
Formation of Two-Step Plasma Electrolytic Oxidation Coating On Commercially Pure Titanium and Study its Properties, M.Sc. Thesis Sharif University of Technology ; Ghorbani, Mohammad
Improvement of biological properties by modifying the composition and morphology of the surface layer is one of the main goals of using plasma electrolytic oxidation (PEO) for coating titanium implants. The purpose of this research is formation of biocompatible coating containing calcium, phosphorus and silicon on titanium by two-step PEO method in DC, constant voltage mode. In addition to good corrosion properties of the resultant coatings in simulated body environment (SBF), Having good adhesion due to the use of electrolytes with useful elements for biological function in both step of coating process rather than acidic electrolytes which are incompatible with the body environment, this...
M.Sc. Thesis Sharif University of Technology ; Najafi, Mehdi
The present study proposes a pricing model for manufacturing and customer support companies which is carried out in the form of multi-level programming. In this model, the manufacturer is considered as the leader and supporting companies as followers. In fact, manufacturer sets up the price level for its customer support first and then according to this price level, customer support companies choose their products and specify the level of after-sales services and the prices. The purpose of this study is to provide insight into the analysis of the after-sales services in a supply chain. The results can be notable for managers in order to demonstrate the impact of different strategies of...
Article Separation and Purification Technology ; Volume 86 , February , 2012 , Pages 143-148 ; 13835866 (ISSN) ; Darvishi, D ; Haghshenas, D. F ; Yousefi, N ; Sadrnezhaad, S. K ; Sharif University of Technology
Re/Mo separation is studied by a new solvent extraction technique which is based on extraction mechanisms of the constituent metals. Based on McCabe-Thiele plots, a flow diagram has been proposed for separation and purification of Re over Mo. Re-recovery section of the diagram shows that Re is extracted when major amount of Mo is removed. For removal of the remained Mo, a two-stage extraction is required at pH = 2 and V a/V o = 1. In order to obtain Re, the resulted aqueous phase is stripped by adding sulfuric acid. According to the results, while more Re is extracted at less pH, optimum extraction of Mo happens at pH = 1.2. Re selectivity over Mo maximizes by approaching of the pH to zero
Article IEEE Workshop on Statistical Signal Processing Proceedings, 28 June 2011 through 30 June 2011, Nice ; June , 2011 , Pages 709-712 ; 9781457705700 (ISBN) ; Babaie Zadeh, M ; Samadi, S ; Jutten, C ; Sharif University of Technology
This paper deals with blind separation of finite alphabet sources where we have n sources and only one observation. The method is applied directly in time (spatial) domain and no transformation is needed. It follows a two stage procedure. In the first stage the mixing coefficients are estimated, and in the second stage the sources are separated using the estimated mixing coefficients. We also study restrictions of this method and conditions for which its performance is acceptable. Simulation results are presented to show the ability of this method to source separation in images and pulse amplitude modulation (PAM) signals
Article Proceedings - IEEE INFOCOM, 26 April 2015 through 1 May 2015 ; Volume 2015-August , 2015 , Pages 498-503 ; 0743166X (ISSN) ; 9781467371315 (ISBN) ; Gao, L ; Huang, J ; Khalaj, B. H ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc 2015
An operator-assisted user-provided network (UPN) has the potential to achieve a low cost ubiquitous Internet connectivity, without significantly increasing the network infrastructure investment. In this paper, we consider such a network where the network operator encourages some of her subscribers to operate as mobile Wi-Fi hotspots (hosts), providing Internet connectivity for other subscribers (clients). We formulate the interaction between the operator and mobile users as a two-stage game. In Stage I, the operator determines the usage-based pricing and quota-based incentive mechanism for the data usage. In Stage II, the mobile users make their decisions about whether to be a host, or a...
Article APCCAS 2008 - 2008 IEEE Asia Pacific Conference on Circuits and Systems, Macao, 30 November 2008 through 3 December 2008 ; January , 2008 , Pages 141-144 ; 9781424423422 (ISBN) ; Bakhtiar, M. S ; Sharif University of Technology
This paper presents a new ADC based on using passive charge sharing SAR ADC in a 2-stage pipeline architecture. The charge domain operation of passive charge sharing ADC poses an inherent limitation on its resolution. The proposed architecture increases the achievable resolution with a low power overhead. Designed and simulated in a 0.18um CMOS process, the 12-bits, 40MS/sec ADC core consumes 7mW from a 1.8V supply
Article 44th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit, Hartford, CT, 21 July 2008 through 23 July 2008 ; 2008 ; 9781563479434 (ISBN) ; Yaghoubi, V ; Sharif University of Technology
In this paper, the rotation of a two-stage turbine rotor is studied. The goal of this article is to present a practical understanding of terminology and behavior based in visualizing how a shaft vibrates, and examining issues that affect vibration. Analytical solutions to predict critical speeds are developed with the aid of the Lagrange method and the Modal analysis. Results are given in tables and diagrams. The matrix solution showed that the critical speeds change as the rotating speed of the shaft increases. It was inferred from the results that even new critical speeds could be generated. Due to the gyroscopic effects, the rotor undergoes some precession which is indicated by the...
SnO2/ZnO double layer thin films: A novel economical preparation and investigation of sensitivity and stability of double layer gas sensors, Article International Journal of Nanomanufacturing ; Volume 2, Issue 1-2 , 2008 , Pages 59-69 ; 17469392 (ISSN) ; Shokuhfar, A ; Sadrnezhaad, S. K ; Shokuhfar, T ; Sharif University of Technology
Inderscience Publishers 2008
A double-layer SnO2/ZnO gas sensor was produced by utilisation of SnOSUB align=right2 and ZnO thin films. Top layer consisted of SnOSUB align=right2 produced by a sol gel-controlled annealing technique. Bottom coating consisted of ZnO thin film precipitated by Two-Stage Chemical Deposition (TSCD) from an aqueous zinc-containing solution. Both top and bottom coatings were analysed by SEM, XRD, EDAX and AAS. Gas sensitivity of the SnO2/ZnO double layer was determined by electrical resistance measurements. Although sensitivity was slightly reduced by double-layer formation, selectivity and stability were considerably improved by combination of the two thin layers. The existence of an...
Article Materials Science and Technology ; Volume 22, Issue 3 , 2006 , Pages 308-314 ; 02670836 (ISSN) ; Sadrnezhaad, S. K ; Sharif University of Technology
A two stage chemical deposition (TSCD) technique is used to produce ZnO films on quartz glass (QG), soda lime glass (SLG) and high purity alumina (HPA) from an aqueous solution of zinc complex. The effects of the substrate material on the chemical composition and morphology of the deposited layer are investigated. The effects of different annealing temperatures (180, 300, 500 and 800°C) on the morphology and orientation of the ZnO crystallites are also determined. X-ray diffraction diffractograms show that above 300°C, the intensity of (002) peak considerably decreases with increasing temperature. Results indicate that changing the substrate from QG to SLG does not significantly influence...
FEM elasto-plastic analysis of a new manufacturing method for covering the free surface of unidirectional composites, Article Computational Materials Science ; Volume 36, Issue 4 , 2006 , Pages 411-424 ; 09270256 (ISSN) ; Adibnazari, S ; Rashidi Moghadam, A ; Sharif University of Technology
Fiber/matrix debonding at the free surface of unidirectional composites deteriorates their performance and ultimately reduces the working life of these materials. Identifying the source, controlling the propagation and elimination of the damages has been the subject of many research attempts. The results show that the singular radial thermal residual stress at the fiber/matrix interface on the free surface of composites is the main reason for initiation of the debonding. Also, it has been experimentally and numerically proven that a thin layer of matrix-like cover on the free surface could highly help in elimination and/or reduction of the damage. However, the results were limited to the...
M.Sc. Thesis Sharif University of Technology ; Haji, Alireza
This Thesis presents a robust network design model for supplying blood during and after an earthquake disaster. A two stage optimization model based on several real-world scenarios is developed. The purpose of this research is to locate and allocate fixed and mobile facilities in probabilistic situation, in which Tehran city with 22 districts is considered as a case study. This model can be categorized as a probabilistic model which demand and supply rate for blood and its derivatives is uncertain. Furthermore the blood transition between different blood types and conversion to its derivatives such as Platelet and plasma are involved in the proposed model. The supply chain for blood consists...