Sharif Digital Repository

Independent Component Analysis (ICA) can be used to decompose functional Magnetic Resonance Imaging (fMRI) data into a set of statistically independent images which are likely to be the sources of fMRI data. After applying ICA, a set of independent components are produced, and then, a "meaningful" subset from these components must be identified, because a large majority of components are non-interesting. So, interpreting the components is an important and also difficult task. In this paper, we propose a criterion based on the entropy of time courses to automatically select the components of interest. This method does not require to know the stimulus pattern of the experiment  

Diffusion imaging with confinement tensor (DICT) is a new model that employs a tensorial representation of the geometry confining the movements of water molecules. The model differs substantially from the commonly employed diffusion tensor imaging (DTI) technique even at small diffusion weightings when the dependence of the signal on the timing parameters of the pulse sequence is concerned. In this work, we assess the accuracy of the two models on a data set acquired from an excised monkey brain. The publicly available data set features differing values for diffusion pulse duration and separation. Our results indicate that the normalized mean squared error is reduced in an overwhelming... 

The Chirikov diffusion in the sphere–ellipsoid binary asteroids through the spin–orbit resonance model is analytically and numerically studied. The primary and the secondary of the binary system are considered sphere and ellipsoid, respectively. The gravitational potential function is expanded up to the fourth-order. The geography of the first- and second-order resonances is derived and studied for different values of asphericity and dynamical flattening of the secondary asteroid and the semimajor axis and eccentricity of the mutual orbit. The Chirikov diffusion due to overlapping of the first- and second-order resonances is examined. For this end, the previously derived criterion for... 

1-D compound metallic grating (CMG) is a periodic structure with more than one slit in each period. When CMG is combined with a graphene sheet as its cover, the incident light is effectively coupled to the plasmons in graphene which in turn can result in strong manipulation of light for both major polarizations. We show that tunable phase resonance and perfect absorption of the incident light are interesting outcomes of this manipulation. In this paper, we demonstrate that fano-like phase resonances which can be observed in CMGs under transverse magnetic polarized incident wave are tuned by changing the Fermi level of graphene. It is shown that while the spectral position of the phase... 

A periodic arrangement of 1-D slits carved in a perfect electric conductor is investigated, and an equivalent model which features sinusoidal surface conductivity on its upper and lower interfaces is derived. Therefore, and in sheer contrast to all the previous attempts that were successful in mimicking only the zeroth-order diffracted waves, it is capable of emulating both specular and nonspecular diffraction orders. The accuracy of the model is verified by the full-wave simulations. The proposed model is used to study the sharp Fano-type extraordinary transmission resonances arising in the structure. The transmission spectrum near these resonances is derived in terms of Fano resonance... 

The staggered quantum walk is a type of discrete-time quantum-walk model without a coin which can be generated on a graph using particular partitions of the graph nodes. We design Hamiltonians for potential realization of the staggered dynamics on a two-dimensional lattice composed of superconducting microwave resonators connected with tunable couplings. The naive generalization of the one-dimensional staggered dynamics generates two uncoupled one-dimensional quantum walks; thus more complex partitions need to be employed. However, by analyzing the coherence of the dynamics, we show that the quantumness of the evolution corresponding to two independent one-dimensional quantum walks can be... 

A new resonance phenomenon is demonstrated in waveguide cavities, which simultaneously uses two orthogonal modes (polarizations). This resonance is formed by bouncing waves with similar handedness, between two simple anisotropic metasurfaces having a relative rotation angle. The rotated anisotropic metasurfaces can cross couple the waves from one polarization to the other at the cavity end. The field profile of the resonant mode does not exhibit nodes and antinodes, thus the resonant frequency is not solely determined by the cavity length, unlike common resonators. The resonance condition is theoretically demonstrated from both field and transmission line perspectives, and is validated by... 

Several parameters, one of which is the Dancoff Factor (DF), are used to calculate the resonance integral (RI) and reduced flux in the resonance region of heterogeneous systems as well as to accurately determine the group constants for criticality calculations. This paper is a report on the development of a program to calculate the DF correction factor using Monte Carlo method and collision probability definition in three-dimensional (3-D) geometries and with multi energy groups. Hence, the DF for any arbitrary arrangement of cylindrical and slab fuel elements is hereby calculated. The fuel elements are monitored and kept at equal levels, though different material compositions and formations... 

In this work, the optical responses of Fe3O4@Au and Fe3O4@Ag are comprehensively investigated using the discrete dipole approximation. It is found that the resonance wavelength and absorption efficiency strongly depend on the composition of the core and shell, geometry of the nanoparticles, core to particle volume ratio, core radius and shell thickness. The strongest impact is due to the shell material, the shape of the nanoparticles and their combination. When the composition of the shell is changed from gold to silver, instead of one fundamental resonance peak the absorption spectrum shows two, corresponding to the bonding plasmon mode at the nanoparticle-environment interface and... 

Due to the fast response of skip cycle modulation technique, it has been used to control of some DC/DC converters. In this paper, it is used to control of a series resonant converter. A pulse generator circuit is presented for zero current switching. Simulation and experimental results are presented to show the features of this control method. Results show that the converter has a fast response and high efficiency. Design notes about magnetic parts of converter are also presented to achieve the highest efficiency  

Coupling of side chain dynamics over long distances is an important component of allostery. Methionine side chains show the largest intrinsic flexibility among methyl-containing residues but the actual degree of conformational averaging depends on the proximity and mobility of neighboring residues. The 13C NMR chemical shifts of the methyl groups of methionine residues located at long distances in the same protein show a similar scaling with respect to the values predicted from the static X-ray structure by quantum methods. This results in a good linear correlation between calculated and observed chemical shifts. The slope is protein dependent and ranges from zero for the highly flexible... 

In Fenton-like oxidation processes, the use of biochar (BC) as support material for the nanoscale zero valent iron-nickel (nZVI-Ni) bimetallic particles attained much attention to activate persulfate (PS) for TCE degradation in aqueous medium. In present work, nZVI-Ni@BC particles with nZVI-Ni to BC mass ratio of 1:5 exhibited excellent results (> 99 % ± 0.24) for TCE degradation. The physico-chemical characteristics, surface morphologies, and elemental mapping of the synthesized nZVI-Ni@BC particles investigated through SEM, EDX, TEM, XPS, XRD, BET and FTIR spectroscopy. For the nZVI-Ni@BC-persulfate system, the effects of PS concentration, initial pH, inorganic ions and natural organic... 

In this study, multivariate classification techniques combined with proton nuclear magnetic resonance (1HNMR) spectroscopy is proposed to identify breast cancer biomarkers that can precisely distinguish between healthy control and breast cancer (BC) patients. In this regard, first optimizing the metabolite extraction procedure was performed using Box-Behnken design (BBD). Then, data-driven soft independent modeling of class analogy (DD-SIMCA) model and partial least squares-discriminant analysis (PLS-DA) were successfully utilized for separating healthy from BC patient's classes. On this matter, both DD-SIMCA and PLS-DA models could successfully distinguish the healthy class from the BC... 

In recent years, the regression dynamic causal modelling (rDCM) method was introduced as a new version of dynamic causal modelling (DCM) to derive effective connectivity in whole-brain networks for functional magnetic resonance imaging (fMRI) data. In this research, we used data obtained while applying the stimulation of audio movie comprised different emotional states. We applied this method to two networks consisting of ten auditory and forty-four regions, respectively. This method was used to study effective connections between emotional states and represent the distinction between emotions. Finally, significant effective connections were found in emotional processing and auditory... 

In this study, a nonlinear absorber that works with a negative stiffness mechanism is suggested to mitigate vibration, and its effect on the reduction of vibration is investigated. The negative stiffness, which is inherently nonlinear, creates internal resonance; therefore, the vibration energy can be transmitted from low-frequency to high-frequency vibrating modes, causing vibration suppression. The nonlinear absorber is added to the primary nonlinear system, and when the main system is subjected to external resonance due to harmonic excitation, the negative stiffness parameter of absorber is so adjusted that autoparametric resonance occurs and vibration is reduced. First, the mathematical... 

Synthesis and immobilization of Au nanoparticles (AuNPs) was performed on transparent fluorine-doped tin oxide (FTO) substrate by pulse electrodeposition method. The method was cost effective, simple and capable of producing nanoparticles strongly attached to the substrate. Effects of several influencing factors such as duty cycle, pulse frequency, current density, solution concentration, deposition period and annealing procedure on the optical properties of AuNPs-FTO electrode were investigated. AuNPs-FTO electrodes were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM) and UV-Vis absorption analysis. Controllability...