Sharif Digital Repository

Synthesis and characterization of a new series of low molecular weight (MW = 500–3000) OH-terminated linear aliphatic unsaturated polyesters based on cis-2-butene-1,4-diol and oxalic to sebacic acid were investigated. Direct polycondensation and transesterification methods were used for the syntheses. The latter was recognized to be the preferable method due to its lower reaction temperature and time, lower diol/diacid ratio, absence of decarboxylation, and formation of a product with low polydispersity (Mw/Mn = 1.3–2.7). Elemental analysis, GPC, FTIR, 1H-NMR, DSC, and WAXD were used for the investigations. A segmented polyurethane based on poly (cis-2-butylene adipate) glycol was also... 

A non-terminated, low molecular weight, highly crystalline, linear aliphatic polyester was successfully synthesized via ester-interchange polycondensation of cis-2-butene-1,4-diol and diethyl oxalate by using of lead (II) oxide as the catalyst. No decarboxylation occurred during the optimized polymerization. Structural and Chemical identification was performed by elemental analysis, FTIR, 'H-NMR, and Mass spectroscopy. Some macrocyle species were detected in the product, according to GPC. Fragmentation patterns were suggested for the main m/e's of the mass spectrum. Thermal characterization was performed by DSC and TGA. It was found that the overall thermal stability of the polyester is... 

Barcoding photons, atoms, and any quantum states can provide a host of functionalities that could benefit future quantum communication systems and networks beyond today's imagination. As a significant application of barcoding photons, we introduce code division multiple-access (CDMA) communication systems for various applications. In this context, we introduce and discuss the fundamental principles of a novel quantum CDMA (QCDMA) technique based on spectrally encoding and decoding of continuous-mode quantum light pulses. In particular, we present the mathematical models of various QCDMA modules that are fundamental in describing an ideal and typical QCDMA system, such as quantum signal... 

We have found the exact (factorized) ground state of a general class of ferrimagnets in the presence of a magnetic field which includes the anisotropic and long-range interactions for arbitrary dimensional space. In particular cases our model represents many spin chains with bond alternation of antiferromagnetic-ferromagnetic coupling, ferrimagnetic spin ladders, and also homogeneous spin- s models. The factorized ground state is a product of single-particle kets on a bipartite lattice composed of two different spins (ρ,σ) which is characterized by two angles, a biangle state. The spin-wave analysis around the exact ground state shows two branch of excitations which are the origin of two... 

Constant volume transparent test combustion chambers are extensively used for investigating injection and fuel burning properties of various combustion engines. Their configuration depends on the engine type and the research purpose. Material of components, shape and dimensions of the chamber and its parts, ease of use, accessibility, sealing and safety of the assembly are the parameters needed to be considered in designing the test cell. This paper explains, structural design of a test combustion chamber and its optical windows using finite element analysis of ANSYS 12.0 software for bearing high pressure variations and thermal shocks of combustion. It was designed for conducting CNG direct... 

Artifact removal is an essential part in electroencephalogram (EEG) recording and the raw EEG signals require preprocessing before feature extraction. In this work, we implemented three filtering methods and demonstrated their effects on the performance of different classifiers. Bandpass digital filtering, median filtering and facet method are three preprocessing approaches investigated in this paper. We used data set lib from the BCI competition 2003 for training and testing phase. Our accuracy varied between 80% and 96%. In our work, we demonstrated that the problems of choosing the classifier and preprocessing methods are not independent of each other. Two of our approaches could achieve... 

In this paper, the performance of five classifiers in P300 speller paradigm are compared. Theses classifiers are Linear Support Vector Machine (LSVM), Gaussian Support Vector Machine (RSVM), Neural Network (NN), Fisher Linear Discriminant (FLD), and Kernel Fisher Discriminant (KFD). In classification of P300 waves, there has been a trend to use SVM classifiers. Although they have shown a good performance, in this paper, it is shown that the FLD classifiers outperform the SVM classifiers. FLD classifier uses only ten channels of the recorded electroencephalogram (EEG) signals. This makes them a very good candidate for real-time applications. In addition, FLD approach does not need any... 

We investigate the phase diagram of an anisotropic ferrimagnetic spin-(1/2, 1) in the presence of a non-commuting (transverse) magnetic field. We find a magnetization plateau for the isotropic case while there is no plateau for the anisotropic ferrimagnet. The magnetization plateau can appear only when the Hamiltonian has the U(1) symmetry in the presence of the magnetic field. The anisotropic model is driven by the magnetic field from the Néel phase for low fields to the spin-flop phase for intermediate fields and then to the paramagnetic phase for high fields. We find the quantum critical points and their dependence on the anisotropy of the aforementioned field-induced quantum phase... 

This paper proposes a new approach to watermarking multimedia products based on the combination of redundant discrete wavelet transform and independent component analysis. The original image is decomposed by RDWT, and watermark is embedded in to LL sub-band frequency according mixing model of the ICA, after that for enhancing the robustness of the watermark, the perceptual model is applied via stochastic approach for watermark adapting. This is based on computation of a noise visibility function (NVF) which has local image properties so the strength of watermarking is controllable. Principal component analysis (PCA) whitening process and FastICA techniques are introduced to ensure a blind... 

A novel method involving focusing of magnetic particles at the inner wall of a curved microchannel and secondary Dean flow-based exchange of their fluid was investigated. Solution exchange occurred in a hybrid microchip at very high throughput and with unprecedented solution exchange and particle isolation efficiencies of 99.2% and 90%, respectively. © 17CBMS-0001  

Bioreactor system has been used in bone tissue engineering in order to simulate dynamic nature of bone tissue environments. Perfusion bioreactors have been reported as the most efficient types of shear-loading bioreactor. Also, combination of forces, such as rotation plus perfusion, has been reported to enhance cell growth and osteogenic differentiation. Mathematical modeling using sophisticated infrastructure processes could be helpful and streamline the development of functional grafts by estimating and defining an effective range of bioreactor settings for better augmentation of tissue engineering. This study is aimed to conduct computational modeling for newly designed bioreactors in... 

Local educational institutions produce in-house English for Specific Purpose (ESP) materials according to the curriculum policies designated and developed by the Ministry of Higher Education In Iran. To this end, this book aims to be used in the Iranian setting at the tertiary level for undergraduate students majoring in Mechanical Engineering. Moreover, the style of English usage in this ESP textbook is American.
Regarding the content of the textbook, it has both thematic organizations in which the topics are relevant and includes sufficient treatment of the target language areas necessary for the students. The principle organizing approach of this textbook is theme-based. In addition,... 

The aim of this study is to employ feedback control loops to provide a stable forward dynamics simulation of human movement under repeated position constraint conditions in the environment, particularly during stair climbing. A ten-degrees-of-freedom skeletal model containing 18 Hill-type musculotendon actuators per leg was employed to simulate the model in the sagittal plane. The postural tracking and obstacle avoidance were provided by the proportional—integral—derivative controller according to the modulation of the time rate change of the joint kinematics. The stability of the model was maintained by controlling the velocity of the body's centre of mass according to the desired centre of... 

A combination of silica chloride and wet SiO2 was used as an effective deacetalizating agent for the conversion of acetals to their corresponding carbonyl derivatives under mild and heterogeneous condition