Sharif Digital Repository

One of the most essential and costly stages in Concrete Face Rockfill Dams (CFRD) construction is to implement the concrete at the upstream face of the dam without joints. As the face concrete is considered as the most integral part to prevent water penetration in CFRDs, it's quality control is of paramount importance. One of the conventional approaches for quality control of the concrete which is used in CFRD is the compressive strength of laboratory samples. The comparison of laboratory and in situ measurements provides information about the accuracy of the obtained results. This research investigates the correlation of concrete compressive strength determined by using different methods in... 

In this paper, we present a decentralized algorithm that computes minimum cost QoS flow subgraphs in network coded multicast networks. These subgraphs are minimum cost solutions that also satisfy user-specified QoS constraints, specifically handling elastic rate and delay demands. Although earlier network coding algorithms in this area have only demonstrated QoS improvements, the proposed QoS network coding is clearly different in the sense that it guarantees that given QoS constraints are met over the network. ©2008 IEEE  

In this paper, we present a new and fast algorithm for generating the seeds set for web crawlers. A typical crawler normally starts from a fixed set like DMOZ links, and then continues crawling from URLs found in these web pages. Crawlers are supposed to download more good pages in less iterations. Crawled pages are good if they have high PageRanks and are from different communities. In this paper, we present a new algorithm with O(n) running time for generating crawler's seeds set based on HITS algorithm. A crawler can download qualified web pages, from different communities, starting from generated seeds set using our algorithm in less iteration  

In this paper, a mathematical model and control theoretical framework for designing AQM controllers in networks supporting TCP Vegas is introduced. We have emphasized on a modified TCP Vegas algorithm that can respond to congestion signals through explicit congestion notification (ECN). The overall nonlinear delayed differential equations of the dynamics model of closed loop system have been derived based on TCP Vegas model. The model is then linearized to derive a transfer function representation between the packet marking probability and the bottleneck router queue length as the input and output of the modified TCP Vegas/AQM system. The model properties have been then examined especially... 

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... 

Nowadays, data and information are recognized as a precious resource in an organization. Data quality indicators help organizations manage the quality of data quantitatively and improve organizational processes. Organizations manage data and information with the help of information systems and make decisions within the framework of data collected and analyzed. On the other hand, continuous evaluation of the quality of data flow in systems can lead to a preventive program to formulate strategies for improving performance. This can be done effectively and efficiently in the form of control charts. In this paper, control charts are employed to monitor the quality of data flow in information... 

Ultrasonic Testing (UT) is one of the most common types of nondestructive methods that is being used in various industries, especially in the automotive industry. In this paper, qualitative and quantitative control of resistance spot welds on three-sheet joints was studied. Initially, mathematical model of ultrasonic waves was extracted for triple sheet joints. Then, acoustic simulation of ultrasonic testing on spot welds was performed using Finite Element Method (FEM). Afterwards, A Multilayer Perceptron (MLP) neural network was used to classify spot welds based on their diameter. There was a mean error of 20.9 % between peak amplitudes of numerical and theoretical models which the most... 

In recent years, utilizing the electrical propulsion system in the marine industry has become widely popular. Control of the propeller has been a high-priority design challenge in this industry. One of the essential issues in propeller control is the speed control of the ships. A suitable control strategy for the propeller should be economically-efficient while ensuring stability, reliability, and power quality of the ship's power system. This article proposes an improved propeller control strategy for increasing/decreasing the ship's speed. This scheme consists of two strategies: a maximum acceleration strategy and an efficient operation strategy. The maximum acceleration strategy aims to... 

Software-defined network (SDN) is an emerging network architecture in which the network control task is separated from packet forwarding. This architecture can be considered as a suitable infrastructure for fifth-generation mobile network (5G) and Internet of things due to its flexibility and dynamism. In real-time networks, time-sensitive packets that miss their deadlines are considered useless or less worthy. As with traditional networks, SDN is expected to support real-time communications and handle a variety of failures (including local controller, switch, and link failures) simultaneously. This study focuses on real-time communication of time-sensitive applications that operate on... 

An efficient isogeometric-based framework is presented to integrate optimum design and formability analysis of sheet metal forming processes. To assess the quality of the formed parts, several objective functions such as fracture, wrinkling, thickness variation, and stretching are studied. In this framework, geometric parameters of addendum surfaces and middle tools are considered as design variables, the objective functions are calculated using the recently developed one-step and multi-step inverse isogeometric methods, and the optimum design variables are obtained using the genetic global optimization algorithm. The major advantage of employing the inverse methods is to analyze the... 

A novel photoacoustic microscopy (PAM) structure, based on Haar wavelet patterns, is proposed in this paper. Its main goal is to mitigate the PAM imaging resolution and thus the time of its sampling process without compromising the image quality. Owing to the intrinsic nature of wavelet transform, this structure collects spatial and spectral components simultaneously, and this feature speeds up the sampling process by 33%. The selection of these patterns helps in better control of required conditions, such as multi-resolution imaging, to guarantee adequate image quality in comparison to previous microscopic structures. Simulation results prove the superior quality of the proposed approach... 

A novel photoacoustic microscopy (PAM) structure, based on Haar wavelet patterns, is proposed in this paper. Its main goal is to mitigate the PAM imaging resolution and thus the time of its sampling process without compromising the image quality. Owing to the intrinsic nature of wavelet transform, this structure collects spatial and spectral components simultaneously, and this feature speeds up the sampling process by 33%. The selection of these patterns helps in better control of required conditions, such as multi-resolution imaging, to guarantee adequate image quality in comparison to previous microscopic structures. Simulation results prove the superior quality of the proposed approach... 

Quality of Experience (QoE) measures the overall quality of a service from users’ point of view by considering several system, human, and contextual factors. There exist various objective and subjective methods for QoE prediction. Although the subjective approach is more expensive and challenging than the objective approach, QoE’s level can be more accurately determined by a subjective test. This paper investigates various features affecting QoE by proposing a comprehensive subjective evaluation. First, we show that many unconsidered factors can significantly affect QoE. We have generated voice samples featuring different values for novel factors related to the speaker, signal, and network.... 

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... 

Image logs provide useful information for fracture study in naturally fractured reservoir. Fracture dip, azimuth, aperture and fracture density can be obtained from image logs and have great importance in naturally fractured reservoir characterization. Imaging all fractured parts of hydrocarbon reservoirs and interpreting the results is expensive and time consuming. In this study, an improved method to make a quantitative correlation between fracture densities obtained from image logs and conventional well log data by integration of different artificial intelligence systems was proposed. The proposed method combines the results of Adaptive Neuro-Fuzzy Inference System (ANFIS) and Neural... 

Control charts are useful tools of monitoring quality characteristics. One of the problems of employing a control chart is that the time it alarms is not synchronic with the time when assignable cause manifests itself in the process. This makes difficult to search and find assignable causes. Knowing the real time of manifestation of assignable cause (change point) helps to find assignable cause(s) sooner and eases corrective actions to be taken. In this paper, a probabilistic neural network (PNN)-based procedure was developed to estimate the variance change point of a normally distributed quality characteristic. The PNN was selected based on trial and error among different types of... 

This Regular evaluation and analysis of river quality helps accurate management to reach acceptable quality. In this study, water quality indices (WQI) method applied to evaluate quality of Jajrood River which is one of the main sources of Tehran drinking water. It helps to subsidize management actions in Jajrood watershed. Sampling carried out for 9 years during 2001-2010 in 10 stations along the river in wet and dry stations to identify water quality and the main source of pollution. Results show water quality in all stations classifies as medium according to National Sanitation Foundation (NSF) and water quality index in wet season is better than the corresponding value in dry seasons.... 

Smoking is known as a major cause of chronic obstructive pulmonary disease (COPD) and hence immediate and effective interventions are required for its elimination. This study aimed to collect valid data with regard to cigarette smoking in adult population of north of Iran for policy making by a meta-analysis of the documents of national non-communicable disease risk factors surveillance system. We investigated relevant evidences by searching in published and non-electronic databases. Data were extracted based on variables such as year of the study, sex, age group and prevalence of smoking habit. Based on results of heterogeneity, we applied fixed or random effects model to estimate the...