Sharif Digital Repository

Engineering, procurement and construction (EPC) contracts are commonly used for the construction of oil and gas production facilities. These projects are subjected to many uncertainties. EPC contractors often assume most of the project risks. Several studies have focused on the identification and analysis of EPC project risks. However, they generally fail to define appropriate and effective risk management strategies. The objective of this study is to define efficient risk mitigation strategies that can be utilized in EPC oil and gas projects. A comprehensive review of literature was conducted to identify the risks in EPC projects. Experts' opinion were used to analyze and categorize these... 

This paper proposes a sublime-optimum soft- computing based controller to follow a desired path with a desired velocity by mobile robots with identified dynamical behavior. This method consists of a fuzzy controller where a trained Neural Network sets its membership functions values in On-line mode. Training of the Network is done by a Genetic Algorithm for various vehicle initial positions and different path convexities in Off-line. After the training of the network, during vehicle motion, it retrieves sub-optimized fuzziness values and sends them to the fuzzy control algorithm according to the vehicle position. Meanwhile, the influential of the path convexity is considered in fuzziness of... 

The effect of vehicles’ compatibility on the odds of death or injury of drivers involved in two-vehicle crashes was investigated. This was done through indexing Crashworthiness (CW) and Crashaggressivity (CA) of major vehicle types. For this purpose, a dataset consisting the information about 551,138 drivers involved in two-vehicle crashes in Iran was used and a two-step analysis framework was employed. In this regard, the Classification and Regression Tree (CART) method was applied in the first step to identify the most significant factors contributing to drivers’ Injury Status (IS). Next, Generalized Estimating Equations (GEE) with a Binomial distribution and a Logit link function were... 

The effect of vehicles’ compatibility on the odds of death or injury of drivers involved in two-vehicle crashes was investigated. This was done through indexing Crashworthiness (CW) and Crashaggressivity (CA) of major vehicle types. For this purpose, a dataset consisting the information about 551,138 drivers involved in two-vehicle crashes in Iran was used and a two-step analysis framework was employed. In this regard, the Classification and Regression Tree (CART) method was applied in the first step to identify the most significant factors contributing to drivers’ Injury Status (IS). Next, Generalized Estimating Equations (GEE) with a Binomial distribution and a Logit link function were... 

The effect of vehicles’ compatibility on the odds of death or injury of drivers involved in two-vehicle crashes was investigated. This was done through indexing Crashworthiness (CW) and Crashaggressivity (CA) of major vehicle types. For this purpose, a dataset consisting the information about 551,138 drivers involved in two-vehicle crashes in Iran was used and a two-step analysis framework was employed. In this regard, the Classification and Regression Tree (CART) method was applied in the first step to identify the most significant factors contributing to drivers’ Injury Status (IS). Next, Generalized Estimating Equations (GEE) with a Binomial distribution and a Logit link function were... 

We report herein the development of a highly sensitive colorimetric method for detection of d-Penicillamine using citrate-capped gold nanoparticles (AuNPs). This assay relies upon the distance-dependent of gold nanoparticles surface plasmon resonance band of gold nanoparticles. By replacing the thiol-containing chelator drug, d-Penicillamine, with citrate on the gold nanoparticles surface, a new peak appearing at a longer wavelength intensifies and shifts further to the red from the original peak position due to aggregation of gold nanoparticles which depends on ionic strength, gold nanoparticles and d-Penicillamine concentration. During this process, the plasmon band at 521 nm decreases... 

Laser assisted machining (LAM) is a promising technology for machining hard to cut materials. In most experimental cases, LAM is undergone in two stages; first, the temperature at the material removal point (Tmr) is tuned by adjusting laser parameters and next, the cutting tool is engaged. Introduction of highly localized heat energy to the workpiece makes the modeling of this process very complicated. Hence, an analytical model for the first stage of the process - rather than multiple experiments or FE modelling - would be beneficial. This article presents an analytical solution to the transient, temperature field in a rotating cylinder subject to a localized laser heat source. The... 

Modeling of the laser-assisted machining (LAM) process requires an accurate estimate of the surface absorption coefficient. In addition to the laser type and material properties, this parameter is dependent on the state of the process in terms of surface quality, texture, oxidation state, and temperature change during the machining process. In this article, two methods are presented for calculating this coefficient based on the surface temperature obtained from measurement by a pyrometer and an analytical model of the process. In the first method, the pyrometer is fixed on a lathe bed while in the second method, a co-moving pyrometer is used. Temperature measurements in both methods are... 

In most image retrieval systems, images include various high-level semantics, called tags or annotations. Virtually all the state-of-the-art image annotation methods that handle imbalanced labeling are search-based techniques which are time-consuming. In this paper, a novel coupled dictionary learning approach is proposed to learn a limited number of visual prototypes and their corresponding semantics simultaneously. This approach leads to a real-time image annotation procedure. Another contribution of this paper is that utilizes a marginalized loss function instead of the squared loss function that is inappropriate for image annotation with imbalanced labels. We have employed a marginalized... 

In this study, scaling effects on fiber metal laminates under tensile and three-point bending tests were investigated numerically and experimentally. The fiber metal laminate specimens were made of aluminum 1050 and unidirectional glass-epoxy. Two scaled sizes of specimens were prepared based on A1n, 0n=90n s. Some specified mechanical properties of these samples were investigated and results showed that fiber metal laminates obey scaling law under quasi-static loading. Explicit finite element code LS-DYNA was utilized for numerical simulation. After validating numerical simulation with experiments, scaling law was studied numerically for four different... 

In this study, a new passive method suitable for geolocating low probability of intercept (LPI) radars is introduced. The method uses two electronic support receivers placed on a fast moving platform (e.g., an airplane or a satellite). The proposed method has a high processing gain, which makes it highly suitable for very weak LPI signals. The method processing gain was analytically derived and illustrated with simulation to determine if the proposed method can detect LPI radars in much lower SNRs compared to regular time-frequency LPI detection methods. Also, the resolution of the proposed method in both range and cross-range directions in radar location finding was analyzed. The results... 

There is a growing interest in developing high-performance sensors monitoring organophosphate pesticides, primarily due to their broad usage and harmful effects on mammals. In the present study, a colorimetric sensor array consisting of citrate-capped 13 nm gold nanoparticles (AuNPs) has been proposed for the detection and discrimination of several organophosphate pesticides (OPs). The aggregation-induced spectral changes of AuNPs upon OP addition has been analyzed with pattern recognition techniques, including hierarchical cluster analysis (HCA) and linear discriminant analysis (LDA). In addition, the proposed sensor array has the capability to identify individual OPs or mixtures of them in... 

Construction managers regularly monitor projects to ensure that the project performance is under control. The earned value method (EVM) is a widely used tool to forecast project cost and time at completion. However, the effectiveness of the EVM in forecasting schedule performance has been questioned particularly because of its inability to address the associated uncertainties and poor performance in predicting project duration. The objective of this study is to present an activity-based model to conduct a probabilistic assessment and estimation of schedule performance in repetitive construction projects. This model, called the Weibull evaluation and forecasting model (WEFM), emphasizes the... 

Most array-based sensing platforms, to date, utilize static response patterns for discrimination of a wide variety of analytes, but only a few studies have focused on the important task of quantitatively resolving structural isomers, which are nowadays important because of their broad usage in medicines and industries. A possible way of accomplishing this feat is to combine kinetic (rather than static) sensor response profiles with the chemical tongue strategy to allow the development of array-based sensors for isomeric discrimination. Here, by adding the time dimension, a simple and novel gold nanorod (AuNR)-based chrono-colorimetric sensor array is proposed for chemical discrimination... 

Building owners’ appropriate risk-mitigation decisions can minimize the social, economic, and socioeconomic consequences of earthquakes. Implementation of appropriate policies can increase the adoption of seismic retrofit measures through the modification of owners’ beliefs. Social interactions among owners can influence their response to the implemented policies. There is a need for appropriate tools that consider the social interactions among the owners and facilitate the evaluation of their response to seismic retrofit promotion policies. The agent-based simulation model in this manuscript addresses this need. The implementation of policies and interactions among agents can influence... 

Building owners’ appropriate risk-mitigation decisions can minimize the social, economic, and socioeconomic consequences of earthquakes. Implementation of appropriate policies can increase the adoption of seismic retrofit measures through the modification of owners’ beliefs. Social interactions among owners can influence their response to the implemented policies. There is a need for appropriate tools that consider the social interactions among the owners and facilitate the evaluation of their response to seismic retrofit promotion policies. The agent-based simulation model in this manuscript addresses this need. The implementation of policies and interactions among agents can influence... 

The widespread use of pesticides in pest management has boosted the demands for developing highly sensitive probes for on-site monitoring. Herein we presented a sensitive enzyme-free ratiometric probe for determination of methyl parathion (MP), as an organophosphate pesticide using TGA-capped CdTe QDs and carbon dots (CDs). Unlike previous methods in which hydrolysis product of MP is instrumental in the response of the sensors, here, self-assembly of cetyltrimethylammonium bromide (CTAB) on the surface of non-modified yellow-emissive CdTe QDs facilitates the quenching of CTAB-QDs upon addition of MP while the fluorescence intensity of CDs remains constant. Using a smartphone, the ratiometric... 

This study presents a framework that utilizes Bayesian regression to create probabilistic cost models for retrofit actions. Performance improvement is the key parameter introduced in the proposed framework. The incorporation of this novel feature facilitates the characterization of retrofit cost as a continuous function of the desired performance improvement. Accounting for the performance gained from retrofit enables the use of the models in determining the optimal level of retrofit. Furthermore, accounting for the model uncertainty facilitates the use of the models in risk and reliability analyses. The proposed framework is applied to create seismic retrofit cost models for masonry school... 

Purpose: Motivated by the high cost of material movements in road construction projects, past studies have used analytical methods to optimize materials logistics plans. A key shortcoming of these methods is their inability to capture the uncertain, dynamic and complex characteristics of the road construction material logistics. Failure to incorporate these characteristics can lead to sub-optimal results. The purpose of this study is to propose the use of discrete event simulation (DES) to address the existing shortfall. Design/methodology/approach: Despite the powerful capabilities of DES models in capturing the operational complexities of construction projects, they have not been... 

Within the past decade, since impediments in nonrenewable fuel sources and the contamination they cause, utilizing green energies, such as those that are sun-oriented, in tandem with electric vehicles, is a developing slant. Coordinating electric vehicle (EV) charging stations with sun-powered boards (PV) reduces the burden of EV charging on the control framework. This paper presents a state-of-the-art literature review on remote control transmission frameworks for charging the batteries of electric vehicles utilizing sun-based boards as a source of power generation. The goal of this research is to advance knowledge in the wireless power transfer (WPT) framework and explore more about...