Sharif Digital Repository

Cutting transport is an important goal in drilling operation especially in horizontal and deviated wells since it can cause problems such as stuck pipe, circulation loss and high torque and drag. To this end, this article focused on the affecting parameters on the cutting transport by computational fluid dynamic (CFD) modeling and real operational data. The effect of drilling fluid and cutting density on the pressure drop, deposit ratio and string stress on the cutting transport has been investigated. A systematic validation study is presented by comparing the simulation results against published experimental database. The results showed that by increasing two times of drilling fluid... 

In this paper a new solution for the single sample problem in low resolution face recognition is proposed. The proposed solution uses an enhanced virtual pose generation method to extend the number of face images of each identity. Using a top-right face image of an identity in the gallery, the method generates other poses of the same identity. Face images are represented as a set of local patches. In order to avoid image alignment problems, patches in the first and second pose are clustered. For each cluster the mapping between the patches of the two poses is learned. Experimental results show superior subjective and objective performance of the proposed method on CASPEAL database compared... 

Evaluating architectures and choosing the correct one is a critical issue in software engineering domain, in accordance with extremely extension of architecturedriven designs. In the first years of defining architecture styles, some special quality attributes were introduced as their basic attributes. After a moment, by utilizing them in practice, some results were obtained confirming some of attributes; some others meanwhile were not witnessed. As software architecture construction process is dependent on and addressed by both usage conditions and quality attributes, in this paper a framework has been proposed to provide an environment and a platform that can cover evaluation of... 

Today, communication science is advancing very rapidly; one of these advances is mobile location determination which means finding position of a mobile station. There are some methods to location determination; one of these methods is Signal Strength (Power of Arrivals). In this research, Mobile Location Determination using enhanced signature database method in a Location grid will be introduced; several ways for positioning error reduction will also be described. © 2009 IEEE  

We consider a basic caching system, where a single server with a database of N files (e.g., movies) is connected to a set of K users through a shared bottleneck link. Each user has a local cache memory with a size of M files. The system operates in two phases: A placement phase, where each cache memory is populated up to its size from the database, and a following delivery phase, where each user requests a file from the database, and the server is responsible for delivering the requested contents. The objective is to design the two phases to minimize the load (peak or average) of the bottleneck link. We characterize the rate-memory tradeoff of the above caching system within a factor of... 

It is of fundamental importance to find algorithms obtaining optimal performance for learning of statistical models in distributed and communication limited systems. Aiming at characterizing the optimal strategies, we consider learning of Gaussian Processes (GP) in distributed systems as a pivotal example. We first address a very basic problem: how many bits are required to estimate the inner-products of some Gaussian vectors across distributed machines? Using information theoretic bounds, we obtain an optimal solution for the problem which is based on vector quantization. Two suboptimal and more practical schemes are also presented as substitutes for the vector quantization scheme. In... 

XML has emerged as a common standard for data exchange over the World Wide Web. One way to manage XML data is to use the power of relational databases for storing and querying them. So the hierarchical XML data should be mapped into flat relational structure. In this paper we propose an algorithm which maps DTD to relational schema and as well as content and structure it preserves the functional dependencies during the mapping process in order to produce relations with less redundancy. This is done by categorizing functional dependencies and introducing four rules to be applied to the relations created by the hybrid inlining algorithm according to each category. These rules will reduce... 

Many websites on the Internet offer services to people. They usually ask the users to fill the registration forms for using their services. Unfortunately, some vandalistic persons write programs which make automatic fake registration. For solving this problem, CAPTCHA (Completely Automated Public Turing test to tell Computers and Human Apart) systems are invented. These systems distinguish human users from computer programs. One of the CAPTCHA methods which is designed for Persian and Arabic users is Nastaliq CAPTCHA. In this method, the image of a Persian or Arabic word which is written in Nastaliq font is chosen from a dictionary, and it is shown to the users, then they are asked to type... 

Skin detection has different applications in computer vision such as face detection, human tracking and adult content filtering. One of the major approaches in pixel based skin detection is using Bayesian classifiers. Bayesian classifiers performance is highly related to their training set. In this paper, we introduce a new Bayesian classifier skin detection method. The main contribution of this paper is creating a huge database to create color probability tables and new method for creating skin pixels data set. Our database consists of about 80000 images containing more than 5 billions pixels. Our tests shows that the performance of Bayesian classifier trained on our data set is better than... 

This paper proposes a distributed attack detection and mitigation technique based on distributed estimation over a multi-agent network, where the agents take partial system measurements susceptible to (possible) biasing attacks. In particular, we assume that the system is not locally observable via the measurements in the direct neighborhood of any agent. First, for performance analysis in the attack-free case, we show that the proposed distributed estimation is unbiased with bounded mean-square deviation in steady-state. Then, we propose a residual-based strategy to locally detect possible attacks at agents. In contrast to the deterministic thresholds in the literature assuming an upper... 

Federated learning (FL) and split learning (SL) are state-of-the-art distributed machine learning techniques to enable machine learning without accessing raw data on clients or end devices. However, their comparative training performance under real-world resource-restricted Internet of Things (IoT) device settings, e.g., Raspberry Pi, remains barely studied, which, to our knowledge, have not yet been evaluated and compared, rendering inconvenient reference for practitioner. This work firstly provides empirical comparisons of FL and SL in real-world IoT settings regarding learning performance and on-device execution overhead. Our analyses demonstrate that the learning performance of SL is... 

Supervised speech emotion recognition requires a large number of labeled samples that limit its use in practice. Due to easy access to unlabeled samples, a new semi-supervised method based on auto-encoders is proposed in this paper for speech emotion recognition. The proposed method performed the classification operation by extracting the information contained in unlabeled samples and combining it with the information in labeled samples. In addition, it employed maximum mean discrepancy cost function to reduce the distribution difference when the labeled and unlabeled samples were gathered from different datasets. Experimental results obtained on different emotional speech datasets... 

We introduce the notion of private set operations (PSO) as a symmetric-key primitive in the cloud scenario, where a client securely outsources his dataset to a cloud service provider and later privately issues queries in the form of common set operations. We define a syntax and security notion for PSO and propose a general construction that satisfies it. There are two main ingredients to our PSO scheme: an adjustable join (Adjoin) scheme (MIT-CSAIL-TR-2012-006 (2012) Cryptographic treatment of CryptDB's adjustable join. http://people.csail.mit.edu/nickolai/papers/popa-join-tr.pdf) and a tuple set (TSet) scheme (Cash, D., Jarecki, S., Jutla, C. S., Krawczyk, H., Rosu, M.-C., and Steiner, M.... 

In this paper, a different interpretation of sustainable transportation, is introduced, in which sustainability with respect to transportation sector for the selected countries is evaluated. This interpretation characterizes "sustainable development" through "harmonic development". It means sustainable development with special focus on transportation can be measured by the degree of conformity between environment, economy, and social aspects on one hand, and transportation on the other hand. The best indicator to perform such a measurement is elasticity. The database used for the study encompasses a series of national indicators for each country Seventy nine countries were initially selected... 

Using stochastic point source and finite fault modeling, the stochastic stress drop is estimated for 52 large shallow earthquakes listed in the 'Pacific Earthquake Engineering Research Center (PEER) Next Generation Attenuation of Ground Motions (NGA)' database. The Pseudo Spectral Acceleration (PSA) of 541 accelerograms, recorded at National Earthquake Hazards Reduction Program (NEHRP) C-class sites from 52 earthquakes are simulated and compared with the PSA listed in the PEER NGA database. The magnitude of the analyzed earthquakes ranged from M4:4 to M7:6. The stress drop is calibrated by trial and error and based on the analysis of residuals where the residual is defined as the log of the... 

The challenges of water resources sustainable development are enormous. Around the globe, the increasing use of water coupled with environmental deterioration calls for sustainable development of the limited water resources. As a significant part of the world's population still lacks access to safe water and adequate sanitation, and as global urbanization continues to increase, continuous, comprehensive, coordinated and cooperative water resources management is required for the sustainable future of urban areas. The objective of this study was to assess water resources sustainable development for selected urban areas around the world. Using centralized databases of international agencies for... 

A dense monitoring network is vital for the reliable assessment of PM10 in different parts of an urban area. In this study, a new idea is employed for the re-construction of the 20 shut-down PM10 monitoring stations of Berlin. It endeavours to find the non-linear relationship between the hourly PM10 concentration of both the still operating and the shut-down PM10 monitoring stations by using a fuzzy modelling technique, called modified active learning method (MALM). In addition, the simulations were performed by using not only raw PM10 databases but also log-transformed PM10 databases for skewness reduction. According to the results of hourly PM10 simulation (root mean square error about... 

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... 

In this paper, we present new adaptive linear discriminant analysis (LDA) algorithm and apply them for adaptive facial feature extraction. Adaptive nature of the proposed algorithm is advantageous for real world applications in which one confronts with a sequence of data such as online face recognition and mobile robotics. Application of the new algorithm on feature extraction from facial image sequences is given in three steps: i) adaptive image preprocessing, ii) adaptive dimension reduction and iii) adaptive LDA feature estimation. Steps 1 and 2 are done simultaneously and outputs of stage 2 are used as a sequence of inputs for stage3. The proposed system was tested on Yale and PIE face... 

The aim of the present study is to provide an Atlas of IRAN Offshore Renewable Energy Resources (hereafter called 'the Atlas') to map out wave and tidal resources at a national scale, extending over the area of the Persian Gulf and Sea of Oman. Such an Atlas can provide necessary tools to identify the areas with greatest resource potential and within reach of present technology development. To estimate available tidal energy resources at the site, a two-dimensional tidally driven hydrodynamic numerical model of Persian Gulf was developed using the hydrodynamic model in the MIKE 21 Flow Model (MIKE 21HD), with validation using tidal elevation measurements and tidal stream diamonds from...