Sharif Digital Repository

In the present paper, a decentralized control algorithm is considered for actively controlling the response of flexible tall building structures under earthquake excitations. Sliding mode control is used as a base control algorithm and a decentralized scheme of that is presented. In the proposed approach, the building is divided into several substructures and for each subsystem a separate local control algorithm is designed. The control algorithm consists of the sliding surface and the reaching law equations. A numerical example is used to demonstrate the efficiency of the control algorithm in guaranteeing the system's global stability under the effects of subsystem interconnections and... 

Although simple additive weighting method (SAW) is the most popular approach for classical multiple attribute decision making (MADM), it is not practical any more if information is fuzzy. The existing methods of Fuzzy Simple Additive Weighting method (FSAW) apply defuzzification which distorts fuzzy numbers. Furthermore, most of the methods usually require lengthy and laborious manipulations. In this paper, we develop a new a fuzzy simple additive weighting method for multiple attribute decision making problems. To avoid defuzzification round off errors caused by multiplication or other arithmetic manipulations, fuzzy numbers are ranked prior to any fuzzy arithmetic in this method. The... 

We propose a ranking method for fuzzy numbers. In this method a preference function is defined by which fuzzy numbers are measured point by point and at each point the most preferred number is identified. Then, these numbers are ranked on the basis of their preference ratio. Therefore, fuzzy numbers are compared relatively and not necessarily one is preferred absolutely over the others. This method is especially designed to evaluate alternatives in multi criteria or multi-attribute decision making. The method is intuitive and can be used to discriminate between numbers easily. The method is specially tailored for triangular fuzzy numbers (TFN) and an algorithm is presented to determine the... 

In an acceptance-sampling plan, where items of an incoming batch of products are inspected one by one, if the number of conforming items between successive non conforming items falls below a lower control threshold, the batch is rejected. If it falls above an upper control threshold, the batch is accepted, and if it lies within the thresholds then the process of inspecting the items continues. The purpose of this article is to develop an optimization model to determine the optimum values of the thresholds such that constraints on the probability of Type I and Type II errors are satisfied. This article starts by developing a Markovian model to derive the expected total cost of the inspection... 

A new approach is developed in this paper to detect general mean shifts of multivariate quality control systems and to determine the quality characteristic(s) responsible for the shift. This approach takes advantage of both a decomposition method and an EWMA-based control statistics that are employed for multivariate normal distributions. In order to evaluate the performance of the proposed methodology, simulation studies are provided to estimate the in- and out-of-control average run lengths under different mean and variance shift scenarios. Simulation experiments are also given to compare the performances of the proposed procedure with the ones of the well-known MEWMA and MCUSUM methods.... 

In this paper, a heuristic threshold policy is developed to detect and classify the states of a multivariate quality control system. In this approach, a probability measure called belief is first assigned to the quality characteristics and then the posterior belief of out-of-control characteristics is updated by taking new observations and using a Bayesian rule. If the posterior belief is more than a decision threshold, called minimum acceptable belief determined using a heuristic threshold policy, then the corresponding quality characteristic is classified out-of-control. Besides using a different approach, the main difference between the current research and previous works is that the... 

The response of large-scale building structures can be actively reduced using an appropriate control algorithm and a number of actuators and sensors located within the building. This paper presents a decentralized control approach for controlling the response of tall buildings. The proposed method aims to divide the structural model into several substructures, each one performing on its own controller algorithm. This approach has already been used in controlling large-scale systems such as power transmission systems and space structures. An instantaneous optimal control scheme is used as the control algorithm with different control feedbacks such as velocity feedback alone and displacement... 

A highly sensitive and selective colorimetric method for detection of copper ions, based on anti-aggregation of D-penicillamine (D-PC) induced aggregated gold nanoparticles (AuNPs) was developed. Copper ions can hinder the aggregation of AuNPs induced by D-PC, through formation of mixed-valence complex with D-PC that is a selective copper chelator. In the presence of a fixed amount of D-PC, the aggregation of AuNPs decreases with increasing concentrations of Cu2+ along with a color change from blue to red in AuNPs solution and an increase in the absorption ratio (A520/A 650). Under the optimum experimental conditions (pH 7, [AuNPs] =3.0 nmol L-1 and [NaCl]=25 mmol L-1), a linear calibration... 

Facility location problem is one of the strategic logistical drivers within the supply chain which is a hard to solve optimization problem. In this study, we focus on the uncapacitated single-source multi-product production/ distribution facility location problem with the presence of set-up cost. To efficiently tackle this decision problem, two Lagrangian-based heuristics are proposed one of which incorporates integer cuts to strengthen the formulation. Local search operators are also embedded within these methods to improve the upper bounds as the search progresses. Three sets of instances with various characteristics are generated and used to evaluate the performance of the proposed... 

Herein, a sensitive, simple, and rapid colorimetric assay for the detection of pamidronate disodium was developed based on the aggregation of citrate-capped gold nanoparticles (AuNPs). This was exploited from the affinity of electron-rich atoms toward the surface of AuNPs, resulting in the aggregation of AuNPs through intermolecular hydrogen bonding interactions. As a result of aggregation under optimum conditions ([NaCl] = 25 mM, [AuNPs] = 3.3 nM and pH 7.0), the color of AuNPs was changed from red to blue and the plasmon band of AuNPs around 520 was decreased along with the formation of a new peak at a longer wavelength in the approximate range of 600 to 700 nm. The intensity ratios of... 

Analytic Hierarchy Process (AHP) is one of the most popular approaches in the area of multiple attribute decision making (MADM). However, it is not practical any more if input information are fuzzy. In this paper, we propose a new method for fuzzy AHP which is especially useful to make decisions for multiple attribute problems. The method is developed by applying preference ratio concept which makes it practical since it assigns crisp weights and crisp scores to different alternatives. Two algorithms are proposed in this paper: The first one defines crisp and normalized weight by pairwise comparison with fuzzy data while the second one calculates fuzzy consistency ratio. The proposed method... 

A new methodology is proposed in this paper to both monitor an overall mean shift and classify the states of a multivariate quality control system. Based on the Bayesian rule (Montgomery, Introduction to statistical quality control, 5th edn. Wiley, New York, USA, 2005), the belief that each quality characteristic is in an out-of-control state is first updated in an iterative approach and the proof of its convergence is given. Next, the decision-making process of the detection and classification the process mean shift is modeled. Numerical examples by simulation are provided in order to understand the proposed methodology and to evaluate its performance. Moreover, the in-control and... 

In this paper, we use both stochastic dynamic programming and Bayesian inference concepts to design an optimum-acceptance-sampling-plan policy in quality control environments. To determine the optimum policy, we employ a combination of costs and risk functions in the objective function. Unlike previous studies, accepting or rejecting a batch are directly included in the action space of the proposed dynamic programming model. Using the posterior probability of the batch being in state p (the probability of non-conforming products), first, we formulate the problem into a stochastic dynamic programming model. Then, we derive some properties for the optimal value of the objective function, which... 

In order to design a decision-making framework in production environments, in this study, we use both the stochastic dynamic programming and Bayesian inference concepts. Using the posterior probability of the production process to be in state λ (the hazard rate of defective products), first we formulate the problem into a stochastic dynamic programming model. Next, we derive some properties for the optimal value of the objective function. Then, we propose a solution algorithm. At the end, the applications and the performances of the proposed methodology are demonstrated by two numerical examples. © 2007 Asian Network for Scientific Information  

To study efficiency of the genetic algorithms (GAs) in optimization of aerodynamic shapes, shape of an airfoil is optimized by a genetic algorithm to obtain maximum lift to drag ratio and maximum lift. The flow field is assumed to be two dimensional, viscous, and transonic and is analyzed numerically. The camber line and thickness distribution of the airfoil are modeled by a fourth order polynomial. The airfoil chord length is assumed constant. Also, proper boundary conditions are applied. A finite volume method using the first order Roe's flux approximation and time marching (explicit) method is used for flow analysis. The simple genetic algorithm (SGA) is used for optimization. This... 

Three steels were designed based on HSLA-100 with additional levels of Mn, Ni, Cr and Cu. The steels were prepared by controlled rolling and tempered at temperatures in range of 550-700°C. The continuous cooling time curves were shifted to longer times and lower temperatures with the increased tendency for the formation of martensite at lower cooling rates. The microstructures revealed that controlled rolling results in austenite with uniform fine grain structure. The steel with the highest amount of Mn showed the greatest strength after tempering at 750 °C. The top strength was attributed to the formation of Cu-rich particles. The steel with 1.03 wt.% Mn, tempered at 650 °C exhibited the... 

Noble metals nanostructures, particularly silver, have attracted much attention in the fields of electronics, chemistry, physics, biology and medicine due to their unique properties which are strongly dependent on the size and shape of metal nanomaterials. This study discusses on silver nanostructures with different geometries including wire, cube, sphere and triangle prepared using solution-phase method and applied for antibacterial activities. X-ray diffraction (XRD), Ultra Violet Visible (UV-Vis) spectroscopy, Dynamic Light Scattering (DLS) and electron microscopy studies of different types of silver nanostructures revealed distinct optical and structural properties of an individual... 

If at least one out of two serial machines that produce a specific product in manufacturing environments malfunctions, there will be non conforming items produced. Determining the optimal time of the machines' maintenance is the one of major concerns. While a convenient common practice for this kind of problem is to fit a single probability distribution to the combined defect data, it does not adequately capture the fact that there are two different underlying causes of failures. A better approach is to view the defects as arising from a mixture population: one due to the first machine failures and the other due to the second one. In this article, a mixture model along with both Bayesian... 

In this research, an iterative approach is employed to analyze and classify the states of uni-variate quality control systems. To do this, a measure (called the belief that process is in-control) is first defined and then an equation is developed to update the belief recursively by taking new observations on the quality characteristic under consideration. Finally, the upper and the lower control limits on the belief are derived such that when the updated belief falls outside the control limits an out-of-control alarm is received. In order to understand the proposed methodology and to evaluate its performance, some numerical examples are provided by means of simulation. In these examples, the... 

In this research, we employ Bayesian inference and stochastic dynamic programming approaches to select the binomial population with the largest probability of success from n independent Bernoulli populations based upon the sample information. To do this, we first define a probability measure called belief for the event of selecting the best population. Second, we explain the way to model the selection problem using Bayesian inference. Third, we clarify the model by which we improve the beliefs and prove that it converges to select the best population. In this iterative approach, we update the beliefs by taking new observations on the populations under study. This is performed using Bayesian...