Sharif Digital Repository

Various physical and biological aspects of the Blood Brain Barrier (BBB) structure still remain unfolded. Therefore, among the several mechanisms of drug delivery, only a few have succeeded in breaching this barrier, one of which is the use of Magnetic Nanoparticles (MNPs). However, a quantitative characterization of the BBB permeability is desirable to find an optimal magnetic force-field. In the present study, a molecular model of the BBB is introduced that precisely represents the interactions between MNPs and the membranes of Endothelial Cells (ECs) that form the BBB. Steered Molecular Dynamics (SMD) simulations of the BBB crossing phenomenon have been carried out. Mathematical modeling... 

Single-time-scale distributed estimation of dynamic systems via a network of sensors/estimators is addressed in this letter. In single-time-scale distributed estimation, the two fusion steps, consensus and measurement exchange, are implemented only once, in contrast to, e.g., a large number of consensus iterations at every step of the system dynamics. We particularly discuss the problem of failure in the sensor/estimator network and how to recover for distributed estimation by adding new sensor measurements from equivalent states. We separately discuss the recovery for two types of sensors, namely α and β sensors. We propose polynomial-order algorithms to find equivalent state nodes in graph... 

Environmental degradation due to economic activities is a key challenge facing sustainable development. The fossil fuel production sector is a very polluting industry. In this research, the future trends of pollution accumulation in the region due to direct/indirect oily discharge into the semi-enclosed area of the Persian Gulf are studied. The purpose of the study was not only to alert policy-makers about potential future threats in the region but also to conduct a trial to develop potential solutions to these problems. Four different environmental cases were studied via the principle of system dynamic modeling simulation. The cases consisted of three situations: relaxed, simple policy, and... 

Considering the problem of funding start-ups because of their nature, some entrepreneurs developed crowdfunding in which funding is done via social network. Crowdfunding is a complicated and dynamic phenomenon. In addition, studies conducted on crowdfunding are not significant in number and they have been conducted in exploratory and partial manner. As a result, it is necessary to adopt an approach capable of understanding complex dynamic phenomena so as to be able to explain a crowdfunding. The present paper designs a system dynamics model of crowdfunding for support of new Iranian knowledge-based IT startups so as to highlight the complexities and dynamics of crowdfunding. The results of... 

In this paper, a new interaction prediction approach is presented for optimal control of nonlinear large-scale systems. The proposed approach uses a new gradient-type coordination scheme which has a larger convergence region with respect to the parameters' variation, and also has a good convergence rate. In this approach, the coordination vector is updated using the gradient of coordination error. This type of coordination considerably reduces the number of iterations. The robustness and the convergence rate of the proposed approach against the best classical interaction prediction approaches are shown through simulations of a benchmark problem. © 2008 IEEE  

Nonlinearity caused by actuator constraint plays a destructive role in the overall performance of a control system. A model predictive controller can handle the problem by implementing a constrained optimization algorithm. Due to the iterative nature of the solution, however, this requires high computation power. In the present work we propose a new method to approach the problem by separating the constraint handling from the predictive control job. The input constraint effects are dealt with in a newly defined component called a predictive directional compensator, which works based on the directionality and predictive concepts. Through implementation of the proposed method, the... 

In this study, a nonlinear observer for high-speed estimation of the sample surface topography in a small duration of the probe transient motion utilizing a 2DOF model of TR-AFM is proposed. Since the time duration to reach the steady-state periodic motion of the oscillating probe in conventional imaging methods is relatively high, the proposed nonlinear observer in this research is able to address this limitation and estimate the surface topography throughout transient oscillation of the microcantilever. With this aim, topography estimation process utilizing a Thau observer without any linearization of the system dynamics is designed and coupled with the system dynamics to achieve sample... 

Over the past few years, due to increasing population, limited water resources, and other pressures on the urban water systems (UWS), urban water management has become a major concern for urban policymakers to develop efficient management solutions. In this study, a new hybrid model called sustainable dynamic urban water metabolism management (SDUWMM) is presented, based on urban water metabolism and system dynamics. Isfahan's UWS has been modeled by SDUWMM and its conditions have been simulated until 2041. SDUWMM considers effective internal relationships of the UWS components such as population, climate change, water supply and demand, infrastructures condition, water price, costs and... 

Ways to reduce an airline's cost has been studied for years. In fact, in order to achieve this goal, ones need to know different types of airline's costs including; fuel and oil, maintenance, Ticketing, passenger services, etc. and their impact on the total cost of an airline. According to announcement of ICAO [1], "maintenance cost (about 11% of total cost) is the second major cost after fuel and oil". Therefore, this may attract airline owners' attention to find ways to control maintenance cost and eventually the total cost of an airline. Though, there are many systematic approaches to analyze cost reduction and making policies, in this article, SD modeling is applied to develop a... 

This paper develops a system dynamics model to analyze the impacts of different kinds of capacity payment as investment incentive mechanisms in Iranian electricity market. Since it is aimed that the incurred capital and operating costs of generation technologies be recovered in Iranian electricity pool, the noncompetitive capacity payment mechanism has been introduced for this purpose in order to encourage new investments in electric power generation system. In the current mechanism, the capacity payments are designated to the generating units in the whole country electricity market. An annual base value of capacity payment is proposed based on recovering the capital cost of a benchmark... 

This study investigates a supply chain of perishable fruits and vegetables. A simulation model using system dynamics approach is proposed to study the behaviors and relationships within the supply chain and to determine the impact of the supply, demand and price interactions. The proposed model yields an insight into the overall agricultural system, taking into account the influence of import quota policies. The purpose of this study is to develop a multi-objective model identifying the best import quota policy for Tehran Municipality Organization of Fruits and Vegetables. The multiple objectives are considered to be price mean, price variation and markup. Key conclusions were reached on how... 

In recent years, subsidy payment has been made a main challenge for governments due to growth of population and energy price in global markets. Targeted subsidy plan has been implemented in Iran since last year, and this article discusses its effects on costs and revenues of Tehran Electricity Company as one of the major subdivisions of Iran's electricity industry. In the new system, structural changes have been made in electricity tariffs, so it is not possible to predict the future trends in electricity consumption only based on the past consumptions. In order to model the decision making structure in the recent conditions, a system dynamics method is applied. In addition to modeling the... 

Offline procedures for estimating parameters of robot dynamics are practically based on the parameterized inverse dynamic model. In this paper, we present a novel approach to parameter estimation of robot dynamics which removes the necessity of parameterization (i.e. finding the minimum number of parameters from which the dynamics can be calculated through a linear model with respect to these parameters). This offline approach is based on a simple and powerful swarm intelligence tool: the particle swarm optimization (PSO). In this paper, we discuss and validate the method through simulated experiments. In "Part Two" we analyze our method in terms of robustness and compare it to robust... 

The inherent complexities of multi-reservoir flood control systems and their operation conditions along with the improvements of optimization methods have led to a positive trend on better development of these models. This trend tends to provide the operators of these systems with more practical solutions. Although optimization models can provide appropriate solutions for operation of multi-reservoir systems, the exact implementation of these solutions in real world is not guaranteed. This arises mainly due to high level risk of flood situation, real time operation constraints, high level uncertainties of inflows that usually are overlooked in optimization models, and so on. These problems... 

In this study the properties of muscle synergies, arising from optimal feedback control are investigated. Three different tasks namely reaching, via-point, and hitting are performed using optimization of corresponding cost functions. Then by applying non-negative matrix factorization method to a dataset of muscle tensions, synchronous muscle synergies are obtained. In this way, different muscle patterns can be generated by linear combination of these basis vectors with non-negative time-varying scaling coefficients. According to our simulations some of obtained muscle synergies are shared between tasks and some of them are specific for one task. This finding is also in agreement with the... 

In this study, a nonlinear observer for high-speed estimation of the sample surface topography in a small duration of the probe transient motion utilizing a 2DOF model of TR-AFM is proposed. Since the time duration to reach the steady-state periodic motion of the oscillating probe in conventional imaging methods is relatively high, the proposed nonlinear observer in this research is able to address this limitation and estimate the surface topography throughout transient oscillation of the microcantilever. With this aim, topography estimation process utilizing a Thau observer without any linearization of the system dynamics is designed and coupled with the system dynamics to achieve sample... 

The present study evaluates the application of top-down steel demand estimation in developing countries. The anticipated steel demand for the case of Iran is calculated by three methods, including the growth model (GM), the intensity of use hypothesis (IUH), and the fixed stock paradigm (FCP). GM shows a broad range of apparent steel demand based on the assumed growth factor. When the gross domestic product (GDP) per capita reaches 13,000 dollars per person (constant 2010 US$), the IUH method estimates the consumption peak consumption at around 500 kg steel per capita per year, which is being expected between 2040 and 2060 depending on the economic growth assumptions. Since fluctuations in... 

In a deregulated environment of power distribution industry, a comprehensive economic evaluation for the implementation of distribution automation (DA) systems is inevitable. Using the presented methodology in this paper and system dynamics approach, it is efficiently possible to deal with variation of the economic parameters such as the interest rate, inflation rate, energy supply cost, load growth, etc. In this paper, economic short-run and long-run impacts of DA systems are evaluated from utility point of view. Also economic benefits from customers' point of view are analyzed. A practical pricing strategy for maximizing the utility profit is suggested depending on the underlying market... 

Background: Nutrigenomic has revolutionized our understanding of nutrition. As plants make up a noticeable part of our diet, in the present study we chose microRNAs of edible plants and investigated if they can perfectly match human genes, indicating potential regulatory functionalities. Methods: miRNAs were obtained using the PNRD database. Edible plants were separated and microRNAs in common in at least four of them entered our analysis. Using vmatchPattern, these 64 miRNAs went through four steps of refinement to improve target prediction: Alignment with the whole genome (2581 results), filtered for those in gene regions (1371 results), filtered for exon regions (66 results) and finally... 

Design technology is expected to rise to electronic system-level (ESL). This necessitates new techniques and tools for synthesizing ESL designs and for verifying them before and after ESL synthesis. A promising verification strategy for future very complex designs is to initially verify the design at the highest level of abstraction, and then check the equivalence of the lower level automatically generated models against that initial golden model. We present one such approach to simulation-based functional verification implemented in our ESL design methodology called ODYSSEY. Our ESL synthesis tool generates a transaction-level model (TLM) at TLM level 2 (i.e., design with partial timing)...