Sharif Digital Repository

A new and simple receiver structure for reducing the multipath inter-symbole interference (ISI) effect is proposed for infrared diffuse links. In this new method, bit-error rate (BER) performance of the system will be improved significantly without any essential change in the receiver structure. In our analysis, all major noise sources such as ambient light, signal shotnoise, dark current and thermal noise of the receiver are considered. © 2009 IEEE  

The aim of this paper is to develop a practical R&D portfolio selection model that addresses effective R&D project valuation issue, while it tackles R&D uncertainty in portfolio optimization. Fuzzy sets theory is employed to capture and model the inaccuracy in project information. To avoid the well-known complications of fuzzy real option valuation, the fuzzy pay-off method is used to more effectively value R&D projects. The resulting problem is formulated as a fuzzy zero-one integer programming model which is later transformed into a crisp mathematical formulation to solve the problem for various degrees of risk. A numerical example is used to illustrate the proposed approach  

In this paper, three critical issues with the paper "A fuzzy set approach for R&D portfolio selection using a real options valuation model", coauthored by Wang and Hwang and published in Omega 2007 are addressed. Shortcomings of the original work are highlighted and corrective measures to improve the approach are proposed  

The objective of this research is to develop a practical research and development (R&D) portfolio selection model that addresses the effective R&D project valuation issue, while tackling R&D uncertainty in portfolio optimization. Fuzzy set theory is employed to capture and model the uncertain project information. To evade the well-known complexities of fuzzy real option valuation, the recently developed fuzzy pay-off method is used to more effectively valuate R&D projects. The resulting problem is formulated as a fuzzy zero-one integer programming model that handles uncertainty of input data in order to determine the optimal portfolio. Two satisfaction measures, which are based on... 

While research into various dimensions of language learning strategies has been thriving over the recent years, grammar learning strategies (GLS) have largely remained under-explored. The present mixed methods research aimed to explore GLS in the three stages of classroom grammar tasks, while striving to determine the sequence of GLS and their contribution to grammar proficiency. In the qualitative phase, 13 participants partook in stimulated recall and semi-structured interviews after completing consciousness-raising (CR) tasks. Then, the grounded theory (GT) methodology was applied to conceptualize a theoretical model. For the quantitative phase, a modified version of Pawlak’s Grammar... 

Due to the pollution of the traditional power generation resources and environmental problems, development of power generation resources has become a major problem in today's world. Because of this reason and economic reasons for fossil fuels, the electricity industry designers and policy-makers are to provide solutions to improve the current situation and to reduce destructive environmental effects. In the meantime, the use of renewable resources such as wind and solar power plants has been a priority of many governments and companies. Because of the uncertainty of the renewable energy resources and their dependence on weather conditions, their influence is along with some problems... 

Recent concerns about environmental conditions have triggered the growing interest in using green energy resources. These sources of energy, however, bring new challenges mainly due to their uncertainty and intermittency. In order to alleviate the concerns on the penetration of intermittent energy resources, this paper investigates impacts of realizing demand-side potentials. Among different demand-side management programs, this paper considers demand response wherein consumers change their consumption pattern in response to changing prices. The research studies demand response potentials from different load sectors on generation system well-being. Consumers’ sensitivity to time-varying... 

The constraints of power saving have compelled SRAM designers to consider sub-threshold area as a viable choice. The biggest barrier of this progress is the stability of SRAM's cells and the correct operations. In this paper a 10T cell structure has been proposed with 90% read and 50% write SNM improvement in comparison to the conventional 6T cell. The hold SNM value is about the 6T cell SRAM. Also using differential read method in the proposed structure causes high read performance and using simpler sense amplifier. The symmetric configuration of this structure helps the SRAM has simpler layout and lower transistor mismatch. Using 90nm TSMC CMOS, 32kb 10T cell SRAM in sub-threshold area is... 

In this study, we performed experiments 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 radius and low... 

Na3MnCO3PO4 (NMCP) is produced by hydrothermal synthesis for rechargeable sodium-ion battery (SIB) cathode. Mechanism of formation of NMCP was investigated by measuring the influence of time and temperature on the rate of production of the NMCP crystallites. X-ray diffraction analysis of the synthesized samples showed that MnCO3 first formed as an intermediate phase. Na3MnCO3PO4 was, however, the last phase retained after 24 h of the hydrothermal process at 120 °C. Sigmoidal shape of the crystallization curves followed the Avrami–Erofeev model which described the chemical kinetics of the Na3MnCO3PO4 formation. Respective apparent activation energies of 29.10 for nucleation and 73.91 kJ/mol... 

Integrated seismic attributes, coherency, acoustic impedance (AI), lambda-rho (λρ) and mu-rho (μρ), were used to delineate and to characterize a complex regional channel deposition system in a carbonate reservoir interval in the upper part of the Sarvak Formation. The study area incorporates three adjacent oil fields in SW Iran (Khuzestan Province) covered by three individual 3D seismic surveys having a total area of about 2800 km 2. We generated a regional horizon-based coherency cube using these three seismic surveys. This revealed a carbonate clastic deposition channelling system over the entire study area. We characterized this channel deposition system in agreement with regional... 

Tortuosity and cementation factor are two critical parameters that significantly affect estimates of reservoir properties. Tortuosity factor can be used to estimate permeability using the Carman-Kozeny equation and is an important parameter for formation resistivity factor calculation using a modified version of Archie's formula. It is also used to predict water saturation of reservoir rocks. Tortuosity as an input parameter in Biot's equation can be used to estimate velocity dispersion. In this work, based on the Generalized Archie Equation Curve Fitting (GAECF), tortuosity and cementation factor are determined for selected intervals in a carbonate reservoir. Formation resistivity factor... 

The fast growth of battery-operated portable applications has compelled the static random access memory (SRAM) designers to consider sub-threshold operation as a viable choice to reduce the power consumption. To increase the hold, read and write static noise margin (SNM) in the sub-threshold regime many structures has been proposed adding extra transistors to the conventional 6T-cell. In this paper we propose a new 8T-cell SRAM that shows 90% improvement in read SNM while write and hold SNM reduction can be ignored (this negligible reduction is due to the two stack transistors in the proposed 8T-cell). Benefiting differential output voltage in the read operation, sense amplifier design is... 

Estimating the feasibility of acid gas geological disposal requires the knowledge of the water content of the gas phase at moderate pressures and temperatures (typically below 50MPa, below 380K) and up to 6mol NaCl. In this paper, a non-iterative model is developed to predict the water content of sour and acid gases at equilibrium with pure water and brine. This model is based on equating the chemical potential of water and using the modified Redlich-Kwong equation of state to calculate the fugacity of the gas phase. The water content of pure CH4, CO2 and H2S are represented with average absolute deviations of less than 3.36, 7.04 and 8.4%, respectively. Experimental data of the water... 

Mechanical alloying and sintering were used to fabricate nanostructured Ti6Al4V scaffolds of highly controllable pore geometry and fully interconnected porous network. Elemental powders were milled for different periods of time (10, 20, 30, 40 and 60 h), mixed with 40-60 vol.-% of 200-400 μm cuboidal NaCl, compacted at 500-600 MPa and sintered according to single or double stage heat treatment regimes at 790 and 950°C under vacuum. After sintering, the samples were soaked in distilled water to washout the NaCl. Foamy microstructures were obtained showing well shaped biopores and fragmentary embedded micropores. The shape of initial NaCl was copied into the biopores which had highly... 

Decreasing Drain-Induced-Barrier-Lowering (DIBL) is one of the nondesirable short-channel effects, causes the threshold voltage of the transistor to be reduced by increasing the drain voltage. DIBL makes it impossible for engineers to consider VT as a constant, and it is necessary to calculate VT as a function of the drain voltage. Therefore, to consider the DIBL effect in the design of ICs, a large computational burden is imposed on the system, which slows down the simulation process in circuit-level simulators. Accordingly, a Nonlinear Feed-Forward Memory-Less (NFFML) model using the Gram-Schmidt orthogonalization approach is proposed, which calculates the VT of the new generation of... 

In reference [1], some weak points in the design of the Shannon stream cipher and a differential distinguisher with complexity of O(214.92) keystream bits (i.e. O(29.92) keystream words) were presented. Another distinguishing attack based on a multidimensional linear transformation was presented in [2] which require 2106.996 keystream words. Both of these attacks need to have access to the initial state that is unlikely. In this paper, a likely attack using fault analysis method is exploited to solve the mentioned problem. Additionally, a new distinguisher is proposed which improves the attack complexity to four times the complexity of running the Shannon stream cipher. Only are two... 

The geometry structures of hexa-coordinated [NiLX]X complexes (X = Cl -, Br-, I-) {L = 8,9,18,19-tetrahydro-7H,17H- dibenzo[f,o] [1,5,9,13]dioxadiaza cyclohexadecine-8,18-diol} are optimized by density functional theory (DFT) using B3LYP/LANL2DZ. The calculated geometric parameters are in good agreement with the corresponding experimental values. Calculation results about these complexes show that dipole moment decreases, and the energy levels of HOMOs descend from iodo-complex to chloro-complex. The energy levels of HOMOs descend gently from iodo-complex to chloro-complex, while the energy levels of LUMOs in the present complexes are almost similar; therefore the energy gapes between HOMOs... 

Pharmaceutical drug Research and Development (R&D) outsourcing to contract research organizations (CROs) has experienced a significant growth in recent decades and the trend is expected to continue. A key question for CROs and firms in similar environments is which projects should be included in the firm's portfolio of projects. As a distinctive contribution to the literature this paper develops and evaluates a business support tool to help a CRO decide on clinical R&D project opportunities and revise its portfolio of R&D projects given the existing constraints, and financial and resource capabilities. A new mathematical programming model in the form of a capital budgeting problem is... 

Lake Urmia is one of the largest hypersaline lakes on earth with a unique biodiversity. Over the past two decades the lake water level declined dramatically, threatening the functionality of the lake’s ecosystems. There is a controversial debate about the reasons for this decline, with either mismanagement of the water resources, or climatic changes assumed to be the main cause. In this study we quantified the water budget components of Lake Urmia and analyzed their temporal evolution and interplay over the last five decades. With this we can show that variations of Lake Urmia’s water level during the analyzed period were mainly triggered by climatic changes. However, under the current...