Sharif Digital Repository

We have studied the isoheight lines on the WO3 surface as a physical candidate for conformally invariant curves. We have shown that these lines are conformally invariant with the same statistics of domain walls in the critical Ising model. They belong to the family of conformal invariant curves called Schramm-Loewner evolution (or SLEκ), with diffusivity of κ∼3. This can be regarded as the first experimental observation of SLE curves. We have also argued that Ballistic Deposition (BD) can serve as a growth model giving rise to contours with similar statistics at large scales. © 2008 The American Physical Society  

We investigate some aspects of the c = -2 logarithmic conformal field theory (LCFT). At first, we calculate some correlators of logarithmic conformal fields which have third order singular OPE with the energymomentum tensor. Then, we argue about the fields in the c = -2 model which are associated with this kind of more general logarithmic primary fields. We go on to find fermionic representations for all the fields in the extended Kac table, in particular the untwisted sector. Moreover, we calculate the various OPEs of the fields, especially for the logarithmic energy-momentum tensor and by using these OPEs we find the exact finite transformation of this field. We briefly discuss about the... 

Correlations between electrical and thermal conduction in polymer composites are blurred due to the complex contribution of charge and heat carriers at the nanoscale junctions of filler particles. Conflicting reports on the lack or existence of thermal percolation in polymer composites have made it the subject of great controversy for decades. Here, we develop a generalized percolation framework that describes both electrical and thermal conductivity within a remarkably wide range of filler-to-matrix conductivity ratios (Y f / Y m), covering 20 orders of magnitude. Our unified theory provides a genuine classification of electrical conductivity with typical Y f / Y m ≥ 10 10 as... 

The fractal structure and scaling properties of a 2d slice of the 3d Ising model is studied using Monte Carlo techniques. The percolation transition of geometric spin (GS) clusters is found to occur at the Curie point, reflecting the critical behavior of the 3d model. The fractal dimension and the winding angle statistics of the perimeter and external perimeter of the geometric spin clusters at the critical point suggest that, if conformally invariant in the scaling limit, they can be described by the theory of Schramm-Löwner evolution (SLE κ) with diffusivity of κ=5 and 16/5, respectively, putting them in the same universality class as the interfaces in 2d tricritical Ising model. It is... 

In this paper, the problem of sending n-bit of data from a client to a server using an asymmetric communication channel is discussed where the line bandwidth from server to client is much higher than that of client to server. The goal is to provide a protocol for this problem so that the average number of actual bits sent by client to server becomes as low as possible. Assuming that data is drawn from an arbitrary distribution D, the average number of bits sent by client to server cannot be less than H(D), where H(D) is the binary entropy of D. This problem was first considered by Adler and Maggs [1]. They assumed that the distribution of D is known only by the server and introduced a... 

Coating of graphite flakes with MgO/carbon nanocomposite was carried out via gaseous state reaction between mixture of Mg metal, CO gas and graphite flakes at 1000 °C. XRD and FE-SEM analysis of coating showed that the coating was comprised of MgO nano particles and amorphous carbon distributed smoothly and covered the graphite surface evenly. Thermodynamic calculations were employed to predict the reaction sequences as well as phase stability. The effect of coating on water wettability and oxidation resistance of graphite was studied using contact angle measurement and TG analysis, respectively. It was demonstrated that the reaction between Mg and CO could result in MgO/C nanocomposite... 

Statistical behavior and scaling properties of isoheight lines in three different saturated two-dimensional grown surfaces with controversial universality classes are investigated using ideas from Schramm-Loewner evolution (SLEκ). We present some evidence that the isoheight lines in the ballistic deposition (BD), Eden and restricted solid-on-solid (RSOS) models have conformally invariant properties all in the same universality class as the self-avoiding random walk (SAW), equivalently SLE8/3. This leads to the conclusion that all these discrete growth models fall into the same universality class as the Kardar-Parisi-Zhang (KPZ) equation in two dimensions  

This paper presents a hybrid adaptive network based fuzzy inference system (ANFIS), computer simulation and time series algorithm to estimate and predict electricity consumption estimation. The difficulty with electricity consumption estimation modeling approach such as time series is the reason for proposing the hybrid approach of this study. The algorithm is ideal for uncertain, ambiguous and complex estimation and forecasting. Computer simulation is developed to generate random variables for monthly electricity consumption. Various structures of ANFIS are examined and the preferred model is selected for estimation by the proposed algorithm. Finally, the preferred ANFIS and time series... 

The configuration of landmarks is an important issue in minimizing the target registration error (TRE). In this paper the effect of different landmark configurations on the accuracy of pedicle screw placement during image guided spine surgery (IGSS) is investigated. Since the spine is deformed in intra-operative conditions compared to the preoperative situation, an accurate alignment of each vertebra is crucial to compensate for the deformation. CT compatible markers are placed over anatomical landmarks which are feasible and routinely used in surgical procedures. The TRE is obtained directly for the markers which are placed on the right and left pedicle of the vertebra. The estimated TRE... 

Experimental investigations are performed in order to determine the thermal conductivity of NiFe2O4 nanoparticles dispersed in deionized water. The magnetic nanoparticles are synthesized using a microemulsion method. The X-ray diffraction (XRD), transmission electronic microscopy (TEM), and vibration sample magnetometer (VSM) are used to characterize the structure, the size and the magnetic properties of the nanoparticles. The VSM results disclose that the NiFe2O4 nanoparticles are ferromagnetic at room temperature. Experimental measurements on thermal conductivity of the prepared nanofluids are conducted at different volume concentrations between 0% and 2% and in the temperature range of... 

The performance of the tower based concentrated solar thermal (CST-tower) plant is very sensitive to the operation strategy of the plant and the incident heat flux on the receiver. To date, most studies have been examined only the design mode characteristics of the cavity receivers, but this paper significantly expands the literature by considering non-design operating conditions of this important sub-component of the CST-tower plants. A feasible non-design operating conditions of the cavity receivers that was considered in this study is the storage mode of operation. Two practical dynamic control strategies were examined then to find the most efficient approach: fixed solar field mass... 

Spinal fusion permanently connects two or more vertebrae in spine to improve stability, correct a deformity or reduce pain by immobilizing the vertebrae through pedicle screw fixation. Pedicle screws should be inserted very carefully to prevent possible irrecoverable damages to the spinal cord. Surgeons use CT/fluoroscopic images to find how to insert the screws safely. However, there is still human error, as determining precise trajectory in 3D space is difficult because of asymmetric structure of pedicle. In this study we attempt to propose a shape based method to help the surgeons to find the more accurate and safe path for screw insertion that minimizes the risk or invasiveness of the... 

The voltammetric behavior of dopamine (DA) and uric acid (UA) on a gold electrode modified with self-assembled monolayer (SAM) of cysteamine (CA) conjugated with functionalized multiwalled carbon nanotubes (MWCNTs) was investigated. The film modifier of functionalized SAM was characterized by means of scanning electron microscopy (SEM) and also, electrochemical impedance spectroscopy (EIS) using para-hydroquinone (PHQ) as a redox probe. For the binary mixture of DA and UA, the voltammetric signals of these two compounds can be well separated from each other, allowing simultaneous determination of DA and UA. The effect of various experimental parameters on the voltammetric responses of DA and... 

Collapsible soils such as loess are particular types of problematic soils, whose collapse potential have caused severe damages to the buildings and structures. Loess is susceptible to large and sudden volume reduction upon wetting in constant normal stress or upon increasing normal stress in constant water content or a combination of these two stress paths. In this research both of these collapse induced paths: wetting and stress paths are investigated on undisturbed specimens of a Loess to observe the effect of various parameters on the collapse behavior of the tested soil., Seven controlled matric suction unsaturated oedometer tests have been conducted on undisturbed specimens taken from... 

In this paper, we find a sample complexity bound for learning a simplex from noisy samples. Assume a dataset of size n is given which includes i.i.d. samples drawn from a uniform distribution over an unknown simplex in RK, where samples are assumed to be corrupted by a multi-variate additive Gaussian noise of an arbitrary magnitude. We prove the existence of an algorithm that with high probability outputs a simplex having a ℓ2distance of at most ε from the true simplex (for any ε > 0). Also, we theoretically show that in order to achieve this bound, it is sufficient to have n ≥ (K eΩ(K/SNR2) samples, where SNR stands for the signal-to-noise ratio. This result solves an open problem in this... 

We study the sample complexity of learning a high-dimensional simplex from a set of points uniformly sampled from its interior. Learning of simplices is a long studied problem in computer science and has applications in computational biology and remote sensing, mostly under the name of “spectral unmixing.” We theoretically show that a sufficient sample complexity for reliable learning of a K-dimensional simplex up to a total-variation error of ε is O(Kε2 log Kε ), which yields a substantial improvement over existing bounds. Based on our new theoretical framework, we also propose a heuristic approach for the inference of simplices. Experimental results on synthetic and real-world datasets... 

We propose a flexible numerical framework for extracting the energy spectra and photon transfer dynamics of a unit kagome cell with disordered cavity-cavity couplings under realistic experimental conditions. A projected-entangled pair state (PEPS) Ansatz to the many-photon wave function allows us to gain a detailed understanding of the effects of undesirable disorder in fabricating well-controlled and scalable photonic quantum simulators. The correlation functions associated with the propagation of two-photon excitations reveal intriguing interference patterns peculiar to the kagome geometry and promise at the same time a highly tunable quantum interferometry device with a signature for the... 

Purpose: The accuracy of pedicle screw placement during image-guided spine surgery (IGSS) can be characterized by estimating the target registration error (TRE). The major factors that influence TRE were identified, minimized, and verified with in vitro experiments. Materials and methods: Computed-tomography- compatible markers are placed over anatomical landmarks of lumbar vertebral segments in locations that are feasible and routinely used in surgical procedures. TRE was determined directly for markers placed on the pedicles of vertebra segments. First, optimum selections of landmarks are proposed for different landmarks according to the minimum achievable TRE values in different... 

At the 16th British Combinatorial Conference (1997), Cameron introduced a new concept called 2-simultaneous coloring. He used this concept to reformulate a conjecture of Keedwell (1994) on the existence of critical partial latin squares of a given type. Using computer programs, we have verified the truth of the above conjecture (the SE conjecture) for all graphs having less than 29 edges. In this paper we prove that SE conjecture is a consequence of the well-known oriented cycle double cover conjecture. This connection helps us to prove that the SE conjecture is true for semieulerian graphs. © 2000 Elsevier Science B.V. All rights reserved  

At the 16th British Combinatorial Conference (1997), Cameron introduced a new concept called 2-simultaneous edge-coloring and conjectured that every bipartite graphic sequence, with all degrees at least 2, has a 2-simultaneous edge-colorable realization. In fact, this conjecture is a reformulation of a conjecture of Keedwell (Graph Theory, Combinatorics, Algorithms and Applications, Proceedings of Third China-USA International Conference, Beijing, June 1-5, 1993, World Scientific Publ. Co., Singapore, 1994, pp. 111-124) on the existence of critical partial latin squares (CPLS) of a given type. In this paper, using some classical results about nowhere-zero 4-flows and oriented cycle double...