Sharif Digital Repository

A new strategy for radiation loss reduction in curved slab waveguides is presented. The proposed strategy is based on the proper modification of the boundary conditions at the core-to-cladding interface, whereupon extremely thin conductive nanolayers with non-zero surface conductance are imposed. The obtained numerical results show a noticeable decrease in the overall loss level. © 2008 The Institution of Engineering and Technology  

Currently, some coarse measures like global network latency are used to compare routing protocols. These measures do not provide enough insight of traffic distribution among network nodes in the presence of different fault regions. This paper presents a detailed traffic analysis of fault-tolerant planar adaptive routing (FTPAR) algorithm achieved by an especially developed tool. Per-node traffic analysis illustrates the traffic hotspots caused by fault regions and provides a great assistance in developing fault tolerant routing algorithms. Based on such detailed information, a simple yet effective improvement of FTPAR is suggested. Moreover, the effect of a traffic hotspot on the traffic of... 

In this paper, the general problem of impedance control for a robotic manipulator with a moving flexible base is addressed. Impedance control imposes a relation between force and displacement at the contact point with the environment. The concept of impedance control of flexible base mobile manipulator is rather new and is being considered for first time using singular perturbation and new sliding mode control methods by authors. Initially slow and fast dynamics of robot are decoupled using singular perturbation method. Slow dynamics represents the dynamics of the manipulator with rigid base. Fast dynamics is the equivalent effect of the flexibility in the base. Then, using sliding mode... 

We consider a planar gravitating thick domain wall of the λφ4 theory as a space-time with finite thickness glued to two vacuum space-times on each side of it. Darmois junction conditions written on the boundaries of the thick wall with the embedding space-times reproduce the Israel junction condition across the wall in the limit of infinitesimal thickness. The thick planar domain wall located at a fixed position is then transformed to a new coordinate system in which its dynamics can be formulated. It is shown that the wall's core expands as if it were a thin wall. The thickness in the new coordinates is not constant anymore and its time dependence is given. © World Scientific Publishing... 

By using the planar laser induced florescence experiment (PLIF), a resorufin (RSRF) dye solution was tested as an oxygen probe. The photoreaction of RSRF dye was investigated and the oxidation process of this fluorescent probe molecule was demonstrated. The effect of the oxygen bubbles on tracing dissolved oxygen was also investigated in this study. Results obtained for this sensitive molecular probe dye are very interesting and verify that such an agent can be used effectively for investigating different interesting phenomena affecting the fluorescence. The temporal and spatial behaviors of the oxidation and fluorescence processes were described in this report. For a delay time of 4500 ms... 

Embedding metrics into constant-dimensional geometric spaces, such as the Euclidean plane, is relatively poorly understood. Motivated by applications in visualization, ad-hoc networks, and molecular reconstruction, we consider the natural problem of embedding shortest-path metrics of unweighted planar graphs (planar graph metrics) into the Euclidean plane. It is known that, in the special case of shortest-path metrics of trees, embedding into the plane requires Θ(√n) distortion in the worst case [19, 1], and surprisingly, this worst-case upper bound provides the best known approximation algorithm for minimizing distortion. We answer an open question posed in this work and highlighted by... 

Planar grating diffraction analysis based on Legendre expansion of electromagnetic fields is reported. In contrast to conventional RCWA in which the solution is obtained using state variables representation of the coupled wave amplitudes; here, the solution is expanded in terms of Legendre polynomials. This approach, without facing the problem of numerical instability and inevitable round off errors, yields well-behaved algebraic equations for deriving diffraction efficiencies, and can be employed for analysis of different types of gratings. Thanks to the recursive properties of Legendre polynomials, for longitudinally inhomogeneous gratings, wherein differential equations with non-constant... 

The goal of this paper is to describe essential criteria for image analysis of planar laser-induced fluorescence (PLIF) signals. A new image file conversion method is introduced and some typical illustrative examples showing the potential applications of the method in PLIF experiments are presented. Analysis of row, column, and total pixel counts, and the dark noise related to an image are discussed. Image segmentation, averaging and background correction can be easily done by the reported method. In our analysis it is straightforward to inspect the pixel counts and check for saturation of the camera sensors. It is also feasible to obtain a particular row or column for interpretation and it... 

Surface modification of SnO2 electron transporting layer (ETL) plays a critical role in the performance of SnO2-based planar perovskite solar cells (PSC). Here, we show how long-time NH4F-based water bath treatment of SnO2 layer makes smoothing and morphological improvements and enhances the device performance. Recently it was shown that short-time NH4F treatment (2 sec) with spin coating method reduces interface traps by improving surface chemistry. Here we observe the smoothing of SnO2 films as a result of long-time NH4F treatment, which could be a result of a slight etching-deposition process. Absorption and resistivity measurements indicate that SnO2 etching process is involved in... 

Here in this research, a modified interface between the electron transport layer (ETL) and the perovskite layer in a perovskite solar cell (PSC) is provided by adding the ammonium chloride (NH4Cl) to the tin oxide (SnO2) as the modified ETL of a planar structure as follows: fluorine-doped tin oxide (FTO)/NH4Cl-SnO2/Mixed cation perovskite/Copper indium disulfide (CIS)/Gold (Au). The effects of NH4Cl on ETL are investigated in different amounts from 0.003 to 0.02 M and the best results were obtained in the amount of 0.013 M. The best NH4Cl-SnO2 ETL could increase the power conversion efficiency (PCE) of fabricated planar PSC by 16.79% with open-circuit voltage (Voc) of 1.15 V and negligible... 

We introduce the concept of local spanners for planar point sets with respect to a family of regions, and prove the existence of local spanners of small size for some families. For a geometric graph G on a point set P and a region R belonging to a family R, we define G∩ R to be the part of the graph G that is inside R (or is induced by R). A local t-spanner w.r.t R is a geometric graph G on P such that for any region R∈ R, the graph G∩ R is a t-spanner for K(P) ∩ R, where K(P) is the complete geometric graph on P. For any set P of n points and any constant ε> 0 , we prove that P admits local (1 + ε) -spanners of sizes O(nlog 6n) and O(nlog n) w.r.t axis-parallel squares and vertical slabs,... 

Hoffmann–Ostenhof's conjecture states that the edge set of every connected cubic graph can be decomposed into a spanning tree, a matching and a 2-regular subgraph. In this paper, we show that the conjecture holds for claw-free subcubic graphs and 4-chordal subcubic graphs. © 2021 Elsevier B.V  

We introduce the concept of local spanners for planar point sets with respect to a family of regions, and prove the existence of local spanners of small size for some families. For a geometric graph G on a point set P and a region R belonging to a family R, we define G∩ R to be the part of the graph G that is inside R (or is induced by R). A local t-spanner w.r.t R is a geometric graph G on P such that for any region R∈ R, the graph G∩ R is a t-spanner for K(P) ∩ R, where K(P) is the complete geometric graph on P. For any set P of n points and any constant ε> 0 , we prove that P admits local (1 + ε) -spanners of sizes O(nlog 6n) and O(nlog n) w.r.t axis-parallel squares and vertical slabs,... 

Hoffmann–Ostenhof's conjecture states that the edge set of every connected cubic graph can be decomposed into a spanning tree, a matching and a 2-regular subgraph. In this paper, we show that the conjecture holds for claw-free subcubic graphs and 4-chordal subcubic graphs. © 2021 Elsevier B.V  

This paper describes a double-cell method, which offers some advantages in image capturing and analysis of the planar laser-induced fluorescence (PLIF) experiments. Double static-cell and circulating-static designs are tested and the fluorescence results are reported. The static-static design offers some advantages when comparing the fluorescence signals for two different dyes, the effect of additives, and of oxidation, whereas the circulating-static design provides an effective method to study the thermal contributions of the measured signal, the photostability of a particular dye, the effect of adding agents, and the quenching effects on a dye under study. In this experiment Rhodamine-WT... 

This method introduces the structural error of regression deviation, which is an effective method for the path generation of a vast type of planar and spatial mechanism. The proposed method avoids point-by-point comparison and requirement of timing and reflects the difference between the two curves very effectively in the objective function. By decreasing the number of the design variables, this method would help considerably in decreasing CPU time. The objective function that is based on regression error would converge to a global minimum by a genetic algorithm. At the end, the effectiveness of the method is shown by two numerical examples. © Sharif University of Technology  

Let Γ(R) be the zero-divisor graph of a commutative ring R. An interesting question was proposed by Anderson, Frazier, Lauve, and Livingston: For which finite commutative rings R is Γ (R) planar? We give an answer to this question. More precisely, we prove that if R is a local ring with at least 33 elements, and Γ(R) ≠ 0, then Γ(R) is not planar. We use the set of the associated primes to find the minimal length of a cycle in Γ(R). Also, we determine the rings whose zero-divisor graphs are complete r-partite graphs and show that for any ring R and prime number p, p ≥ 3, if Γ(R) is a finite complete p-partite graph, then Z(R) = p2, R = p3, and R is isomorphic to exactly one of the rings ℤp3,... 

Triboelectric nanogenerators (TENG) have been reported with attractive benefits such as adaptability, lightweight, and simple integration, are interesting for self-powered sensor design. Herein, an innovative magnetically circular layers TENG (MCL-TENG) are reported for velocity sensing and damage detection. The key role of this structure is the magnets fixed on the device, providing attractive force to move. The electrical performance of MCL-TENG under loading condition is investigated experimentally. According to the structure of the magnetic system, the MCL-TENG can effectively react to a frail striking and can be utilized to consider the speed parameters and detecting crack without the... 

We study the quantum nonlinear planar Hall effect in bilayer graphene under a steady in-plane magnetic field. When time-reversal symmetry is broken by the magnetic field, a charge current occurs in the second-order response to an external electric field as a result of the Berry curvature dipole in momentum space. We show that a nonlinear planar Hall effect originating from the anomalous velocity is caused by an orbital effect of an in-plane magnetic field on electrons in bilayer graphene in the complete absence of spin-orbit coupling. Taking into account the symmetry analysis, we derive the dominant dependence of the Berry curvature dipole moment on the magnetic field components. Moreover,... 

In the Partial Vertex Cover (PVC) problem, we are given an n-vertex graph G and a positive integer k, and the objective is to find a vertex subset S of size k maximizing the number of edges with at least one end-point in S. This problem is W[1]-hard on general graphs, but admits a parameterized subexponential time algorithm with running time 2O(k)nO(1) on planar and apex-minor free graphs [Fomin et al. (FSTTCS 2009, IPL 2011)], and a kO(k)nO(1) time algorithm on bounded degeneracy graphs [Amini et al. (FSTTCS 2009, JCSS 2011)]. Graphs of bounded degeneracy contain many sparse graph classes like planar graphs, H-minor free graphs, and bounded tree-width graphs (see Fig. 1). In this work, we...