Sharif Digital Repository

Hydrogen and syngas, as two effective clean fuels, have a considerable stake in the global fuel market. These are dominantly produced from fossil fuels through reforming processes, which lose a large amount of energy and emit numerous amounts of CO2. Bio-renewable glycerol steam reforming is an attractive alternative to traditional reforming for reducing the dependence on hydrocarbon resources and mitigating climate change. This research aims to manage a heat-integrated reactor with three concentric cylinders, containing exothermic-side (methane tri-reforming), endothermic-side (glycerol steam reforming), and permeation-side for co-production of pure hydrogen and syngas. In this process,... 

This paper presents a Multiplicative Patchwork Method (MPM) for audio watermarking. The watermark signal is embedded by selecting two subsets of the host signal features and modifying one subset multiplicatively regarding the watermark data, whereas another subset is left unchanged. The method is implemented in wavelet domain and approximation coefficients are used to embed data. In order to have an error-free detection, the watermark data is inserted only in the frames where the ratio of the energy of subsets is between two predefined values. Also in order to control the inaudibility of watermark insertion, we use an iterative algorithm to reach a desired quality for the watermarked audio... 

This research aims two major objectives: first, the influence of respiration on the particles concentration is investigated numerically in a cleanroom with a specified geometry and second, the respiration and the manner of particles diffusion are simulated. Generally, in many hospital cleanrooms such as the open-heart surgery, organ transplantation and neurosurgery rooms, reduction of the pollutant particles is important as a factor that can lead to capillary clogging during operation. In addition, the significance of reducing the concentration of large particles reveals more according to the fact that dust particles may act as a means for various pathogenic bacteria and viruses. Every... 

This research aims two major objectives: first, the influence of respiration on the particles concentration is investigated numerically in a cleanroom with a specified geometry and second, the respiration and the manner of particles diffusion are simulated. Generally, in many hospital cleanrooms such as the open-heart surgery, organ transplantation and neurosurgery rooms, reduction of the pollutant particles is important as a factor that can lead to capillary clogging during operation. In addition, the significance of reducing the concentration of large particles reveals more according to the fact that dust particles may act as a means for various pathogenic bacteria and viruses. Every... 

A Multiplicative Patchwork Method (MPM) for audio watermarking is proposed in this paper. In order to embed watermark data within the host signal, two subsets of the host signal features are selected using two secret keys. Then, watermark data is inserted simply by multiplying one subset and leaving the other one unchanged. In order to have an error free detection in attack-free case, embedding is performed in the selected frames of the host signal which satisfies a certain condition. This method is implemented in the wavelet domain and approximation coefficients are used for data embedding. Furthermore, the inaudibility of watermark insertion is controlled using iterative approach aided by... 

In this paper an accurate real-time sequence-based system for representation, recognition, interpretation, and analysis of the facial action units (AUs) and expressions is presented. Our system has the following characteristics: 1) employing adaptive-network-based fuzzy inference systems (ANFIS) and temporal information, we developed a classification scheme based on neuro-fuzzy modeling of the AU intensity, which is robust to intensity variations, 2) using both geometric and appearance-based features, and applying efficient dimension reduction techniques, our system is robust to illumination changes and it can represent the subtle changes as well as temporal information involved in formation... 

Facial Action Coding System consists of 44 action units (AUs) and more than 7000 combinations. Hidden Markov models (HMMs) classifier has been used successfully to recognize facial action units (AUs) and expressions due to its ability to deal with AU dynamics. However, a separate HMM is necessary for each single AU and each AU combination. Since combinations of AU numbering in thousands, a more efficient method will be needed. In this paper an accurate real-time sequence-based system for representation and recognition of facial AUs is presented. Our system has the following characteristics: 1) employing a mixture of HMMs and neural network, we develop a novel accurate classifier, which can... 

Currently, ammonia, as a clean and sustainable energy carrier, is intensively synthesized from its elements during the Haber-Bosch technology. This process requires a large amount of energy and emits numerous amounts of carbon dioxide, because hydrogen is dominantly produced from fossil fuels through reforming processes. Biomass-derived glycerol steam reforming is an attractive alternative to traditional reforming for reducing the dependence on hydrocarbon resources and mitigating climate change. This research aims to intensify a heat-integrated process for the co-production of ammonia and syngas from glycerol valorization. In this process, glycerol reforming continuously provides hydrogen... 

Catalytic reduction of nitrobenzene is the leading technological step in aniline production. The hydrogen required for this stage, is dominantly produced from fossil fuels through reforming processes, which take much energy and emit large amounts of CO2. Biomass-derived glycerol steam reforming is an attractive alternative to traditional reforming to reduce the dependence on hydrocarbon resources and mitigate climate change. This research aims to analyze a mass- and heat-integrated multi-tubular membrane reactor, containing nitrobenzene hydrogenation (exothermic-side) and glycerol steam reforming (endothermic-side) for co-production of aniline and syngas. In this process, hydrogenation... 

In this paper a novel method called Extended Two-Dimensional PCA (E2DPCA) is proposed which is an extension to the original 2DPCA. We state that the covariance matrix of 2DPCA is equivalent to the average of the main diagonal of the covariance matrix of PCA. This implies that 2DPCA eliminates some covariance information that can be useful for recognition. E2DPCA instead of just using the main diagonal considers a radius of r diagonals around it and expands the averaging so as to include the covariance information within those diagonals. The parameter r unifies PCA and 2DPCA. r=1 produces the covariance of 2DPCA, r=n that of PCA. Hence, by controlling r it is possible to control the... 

Objectives: The aim of this study was to investigate the effects of implant design on the apex area and on stress and stress patterns within surrounding bone. Methods: Three commercially available implants with the same diameter (3.5 mm), same length (10-11 mm), and same complement abutment were selected for modeling as follows: (1) flat apical design with light tapering degree, (2) dome-shaped apical design with light tapering, and (3) flat apical design with intense tapering in one-third of the apical area. According to human cone-beam computed tomography (CBCT), the bone was modeled using a cortical thickness of 2 mm and cancellous bone. Forces of 100 N and 300 N in the vertical and 15°... 

Several methods have been proposed and explored to improve the performance of the energy storage unit. This work numerically investigates the melting process of a phase change material in a rectangular enclosure in presence of an auxiliary fluid considering different volume ratios. This investigation aims to obtain the volume ratio at which the amount of energy storage in the system becomes optimized for a specified time period. Oleic acid with a melting point of 13.5 °C is selected as the phase change material and water as a fluid with a higher density than oleic acid is chosen as the auxiliary fluid. Imposing the auxiliary fluid on top of the oleic acid, a displacement occurs between the... 

This paper presents a novel approach to audio signals watermarking in the wavelet or the Walsh transform domain. The idea is to embed watermark data in the coefficients of some scales of the transform domain. The overall bit rate of this method is about 90 bps. Due to low computational complexity of the suggested approach, particularly in the Walsh domain, this algorithm can be implemented in real time. Experimental results show robustness of the proposed method in low SNRs and also against some typical attacks, such as MP3 compression, echo, filtering, etc. Subjective evaluation confirms transparency of the watermarked audio signals. © 2006 IEEE  

The aim of this study was to use finite element analysis (FEA) to assess the influence of microthread design at the implant neck on stress distribution in the surrounding bone. A commercially available implant with 3.5 mm diameter and 10.5 mm length was selected and used as a model. For the purpose of designing the microthread implant model, microthreads were added to the implant neck in a computerized model. A force measuring 100 N was then applied to the entire surface of the abutment in the vertical direction. The results showed that in both models, stress was mainly concentrated at the cortical bone adjacent to the neck of the implant. Maximum stress values in the cortical bone... 

In this paper, the synchronization of a pair of pacemaker cells as Sino-Atrial (SA) and Atrio-Ventricullar (AV) nodes have been studied and a new approach for synchronization, based on the concept of Phase Response Curve (PRC), has been proposed. The paper starts with presenting the necessary and sufficient conditions for synchronization in terms of the PRC parameters. Such conditions are time dependent and thus, the paper proceeds with deriving some sufficient conditions, which are not time dependent. The time-delay between the firing time of SA node and when it reaches the AV node is also considered. When the conditions for spontaneous synchronization are not valid, the synchronization is... 

In this study a synchronization method is developed to prevent the blocking arrhythmias which are caused by lack of synchronization between the two major heart pacemakers called the Sino-Atrial (SA) node and Atrio-Ventricullar (AV) node. Such pacemakers can be modeled by the Van der Pol oscillators. Feedback linearization method is used in synchronization. Since all states are not always available, they are estimated by a new observer in this research. To design the observer, first we introduce a robust observer for a unique Van der Pol oscillator. The robustness of proposed observer is obtained using gain and phase margins test. The observer variables are such that the error dynamical... 

In this paper, our main purpose is to embed data in the frequency domain of audio signals. Data was embedded by means of Quantization Index Modulation (QIM) in the frequency domain. With this aim, the spectrum of the audio signal was divided into two parts. The first part consisted of the first 19 Barks and the second included the remaining 6 Barks. Each of these parts had a different quantization step size. In order to have large quantization step sizes which yield more robustness, Human Auditory System (HAS) has been used. Decoder detects the watermark signal, without using the original audio signal. Simulation results have shown that this watermarking scheme has better robustness against...