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The minimum vulnerability problem
, Article Algorithmica ; Volume 7676 LNCS , 2012 , Pages 382-391 ; 14320541(ISSN) ; 9783642352607 (ISBN) ; Emamjomeh Zadeh, E ; Norouzi Fard, A ; Yazdanbod, S ; Zarrabi Zadeh, H ; Sharif University of Technology
2012
Abstract
We revisit the problem of finding k paths with a minimum number of shared edges between two vertices of a graph. An edge is called shared if it is used in more than one of the k paths. We provide a ⌊k/2⌋-approximation algorithm for this problem, improving the best previous approximation factor of k - 1. We also provide the first approximation algorithm for the problem with a sublinear approximation factor of O(n3/4), where n is the number of vertices in the input graph. For sparse graphs, such as bounded-degree and planar graphs, we show that the approximation factor of our algorithm can be improved to O(√n). While the problem is NP-hard, and even hard to approximate to within an O(log n)...
Computation of lucky number of planar graphs is NP-hard
, Article Information Processing Letters ; Volume 112, Issue 4 , February , 2012 , Pages 109-112 ; 00200190 (ISSN) ; Dehghan, A ; Kazemi, M ; Mollaahmadi, E ; Sharif University of Technology
2012
Abstract
A lucky labeling of a graph G is a function l:V(G)→N, such that for every two adjacent vertices v and u of G, σ w∼vl(w)≠ σ w∼ul(w) (x∼y means that x is joined to y). A lucky number of G, denoted by η(G), is the minimum number k such that G has a lucky labeling l:V(G)→{1,⋯,k}. We prove that for a given planar 3-colorable graph G determining whether η(G)=2 is NP-complete. Also for every k≥2, it is NP-complete to decide whether η(G)=k for a given graph G
Tunneling properties of nonplanar molecules in a gas medium
, Article Physical Review A - Atomic, Molecular, and Optical Physics ; Volume 84, Issue 6 , 2011 ; 10502947 (ISSN) ; Bassi, A ; Sharif University of Technology
Abstract
We propose a simple, general, and accurate formula for analyzing the tunneling between classical configurations of a nonplanar molecule in a gas medium, as a function of the thermodynamic parameters of the gas. We apply it to two interesting cases: (i) the shift to zero frequency of the inversion line of ammonia, upon an increase in the pressure of the gas; and (ii) the destruction of the coherent tunneling of D 2S 2 molecules in a He gas. In both cases, we compare our analysis with previous theoretical and experimental results
Decomposing claw-free subcubic graphs and 4-chordal subcubic graphs
, Article Discrete Applied Mathematics ; Volume 296 , 2021 , Pages 52-55 ; 0166218X (ISSN) ; Ahanjideh, M ; Akbari, S ; Sharif University of Technology
Elsevier B.V
2021
Abstract
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
Decomposing claw-free subcubic graphs and 4-chordal subcubic graphs
, Article Discrete Applied Mathematics ; Volume 296 , 2021 , Pages 52-55 ; 0166218X (ISSN) ; Ahanjideh, M ; Akbari, S ; Sharif University of Technology
Elsevier B.V
2021
Abstract
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
Application of double-cell arrangement in planar laser-induced fluorescence experiments
, Article Review of Scientific Instruments ; Volume 76, Issue 8 , 2005 , Pages 1-5 ; 00346748 (ISSN) ; Ahmadi, H ; Razani, M ; Sharif University of Technology
2005
Abstract
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...
Millimeter-wave artificial dielectric waveguides for integrated applications
, Article IEEE MTT-S International Microwave and RF Conference 2014, IMaRC 2014 - Collocated with Intemational Symposium on Microwaves, ISM 2014, 15 December 2014 through 17 December 2014 ; 2015 , Pages 225-228 ; 9781479963164 (ISBN) ; Rejaei, B ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2015
Abstract
High-quality guided wave devices are key components in integrated millimeter-wave circuits. In this paper, we propose mm-wave planar dielectric waveguides based on thin, anisotropic artificial dielectric layers with very high in-plane permittivity. Waves propagating on such films are surface waves whose field exponentially decays outside the film in the vertical direction, similar to waveguides commonly used in integrated optics. The very high in-plane permittivity of the artificial dielectric layers leads to strong field confinement, and allows the implementation of relatively thin waveguides. This fact, together with the planar structure of these devices, make them highly suitable for...
Magnetically circular layers triboelectric nanogenerators (MCL-TENG) for velocity sensing and damage detection
, Article Sustainable Energy Technologies and Assessments ; Volume 53 , 2022 ; 22131388 (ISSN) ; Matin Nazar, A ; Egbe, K. J. I ; Rayegani, A ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
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...
Design and Analysis of Vibration-Based, Friction-Drive Micro-Mechanisms for Planar, Nano-Scale Locomotion
, M.Sc. Thesis Sharif University of Technology ; Vossoughi, Gholamreza (Supervisor)
Abstract
Design and modeling of a micromechanism for generating planar, nano-scaled locomotion is the subject of this thesis. First, we introduced the concepts and fundamental definitions used throughout the thesis. Then, based on the classification of the locomotion principles employed in microrobots, the related literature about design and fabrication of different microrobots is investigated. Inertial slip generation and contact force variation, as the preferred group, is utilized for further analysis. Since friction force is the main propelling source in the microrobot’s locomotion principle, different models proposed for this phenomenon are investigated and the Coulomb friction model is selected...
Analysis of Artificial Dielectric Waveguides for Millimeter Wave Applications
, Ph.D. Dissertation Sharif University of Technology ; Rejaei, Behzad (Supervisor)
Abstract
Millimeter wave technology may prove to be one of the key technologies of the 21st century, covering a broad range of applications including high-speed telecommunication, wireless sensing, and ultra-fast digital computing. The ultimate (commercial) success of these technologies depends on the ability to integrate mm-wave circuitry on a chip, bringing about significant size and cost reduction. Traditionally, mm-wave systems have made extensive use of waveguides based on hollow- or dielectric-filled metallic cavities for the transfer and processing of signals. Cavity waveguides exhibit very low loss, but are not well-suited to high volume manufacturing or on-chip integration due to their...
A Survey on Min-cut On Planar Graphs
, M.Sc. Thesis Sharif University of Technology ; Foroughmand Arabi, Mohammad Hadi (Supervisor)
Abstract
In minimum cut problem we aim at finding a set of edges with minimum overall cost possible, such that removing them would separate two specific vertices, source and sink. This problem has been studied thoroughly, however the available algorithms were not proven to be time-wise optimal. Nowadays, planar graphs have attracted more attention because of their applications in cities and countries map. Moreover,their characteristics and properties, make some problems easier to solve in planar case. In this thesis, we will have a survey on algorithms for minimum cut on planar graphs. Our motivation to choose these algorithms is the balance between how easily they could be implemented and how fast...
Design and Implementation of a High-Efficient High-Power-Density Telecom Battery Charger using Planar Matrix Transformers
, M.Sc. Thesis Sharif University of Technology ; Tahami, Farzad (Supervisor)
Abstract
In creating a telecom battery charger there are three challenging factors which are high power density, high efficiency and modularity. A telecome battery charger consist of a rectifier with power factor correction capability and a DC-DC converter. The power stage of DC-DC converter with high output current and low output voltage has a vital role in the battery charger. The isolation transformer and magnetic component of LLC resonant tank are two huge and heavy parts of the DC-DC converter. With the emergence of GaN and SiC switches pushing frequency to to megahertz is possible which resulted in decreasing the volume of passive divices. But with increasing the frequency, designing of the...
The potentiostatic electrodeposition of gold nanowire/nanotube in HAuCl4 solutions based on the model of recessed cylindrical ultramicroelectrode array
, Article Journal of the Electrochemical Society ; Volume 160, Issue 6 , 2013 , Pages D279-D288 ; 00134651 (ISSN) ; Dolati, A ; Siavash Moakhar, R ; Sharif University of Technology
2013
Abstract
The mechanism of gold nanowire (AuNW) and nanotube (AuNT) electrodeposition in a cyanide-free solution is investigated for the first time based on the analytical model of Szabo et al. (A. Szabo et al., J. Electroanal. Chem. 217 (1987) 417) for recessed cylindrical ultramicroelectrode (UME). Track-etched Polycarbonate Template (PCT) is served as cylindrical UME ensemble/arrays. Firstly, Au is nucleated through a charge transfer step and when the Nernst thickness exceeds the pore length, the radial diffusion is established around pore mouths. By overlapping of these domains, the planar diffusion toward the whole PCT surface is obtained. An analytic expression for global diffusion coefficient...
The complexity of the proper orientation number
, Article Information Processing Letters ; Volume 113, Issue 19-21 , 2013 , Pages 799-803 ; 00200190 (ISSN) ; Dehghan, A ; Sharif University of Technology
2013
Abstract
A proper orientation of a graph G=(V,E) is an orientation D of E(G) such that for every two adjacent vertices v and u, dD -(v) ≠ dD -(u) where dD -(v) is the number of edges with head v in D. The proper orientation number of G is defined as χ→(G)=minD∈Γmaxv∈V(G)d D -(v) where Γ is the set of proper orientations of G. We have χ(G)-1≤χ→(G)≤Δ(G), where χ(G) and Δ(G) denote the chromatic number and the maximum degree of G, respectively. We show that, it is NP-complete to decide whether χ→(G)=2, for a given planar graph G. Also, we prove that there is a polynomial time algorithm for determining the proper orientation number of 3-regular graphs. In sharp contrast, we will prove that this problem...
A novel approach to array steering vector estimate improvement
, Article 2000 10th European Signal Processing Conference, EUSIPCO 2000, 4 September 2000 through 8 September 2000 ; Volume 2015-March, Issue March , 2015 ; 22195491 (ISSN) ; Champagne, B ; Valaee, S ; Sharif University of Technology
European Signal Processing Conference, EUSIPCO
2015
Abstract
In this paper, we present a method for estimating the signal sources steering vector using an arbitrary planar array with omnidirectional elements. The proposed method improves the initial estimation of the signal steering vector in two steps. In the first step of this algorithm we minimize of the distance between the steering vector and the signal subspace. The second step improves the estimation of the first step using a defined cost function which is based on a structural criterion for signal steering vector. Simulation results show the capability of the proposed signal steering vector estimate improvement
Spatial integration by a dielectric slab and its planar graphene-based counterpart
, Article Optics Letters ; Volume 42, Issue 10 , 2017 , Pages 1954-1957 ; 01469592 (ISSN) ; Khavasi, A ; Sharif University of Technology
Abstract
In this contribution a new approach to perform spatial integration is presented using a dielectric slab. Our approach is indeed based on the fact that the transmission coefficient of a simple dielectric slab at its mode excitation angle matches the Fourier-Green's function of first-order integration. Inspired by the mentioned dielectric-based integrator, we further demonstrate its graphene-based counterpart. The latter is not only reconfigurable but also highly miniaturized in contrast to the previously reported designs [Opt. Commun. 338, 457 (2015)]. Such integrators have the potential to be used in ultrafast analog computation and signal processing. © 2017 Optical Society of America
Excitation and propagation of surface polaritonic rogue waves and breathers
, Article Physical Review A ; Volume 98, Issue 1 , 2018 ; 24699926 (ISSN) ; Sadighi Bonabi, R ; Sanders, B. C ; Sharif University of Technology
American Physical Society
2018
Abstract
Excitation and propagation of the surface polaritonic rogue waves and breathers are investigated by proposing a coupler free optical waveguide that consists of a transparent layer, middle negative index metamaterial layer, and bottom layer of the cold four level atomic medium. In this planar optical waveguide, a giant controllable Kerr nonlinearity is achieved by sufficient field concentration and a proper set of intensities and detunings of the driven laser fields. As a result, various kinds of temporal surface polaritonic solitons, rogue waves, and breathers can be propagated in the narrow window for electromagnetically induced transparency. We find that the giant intensity and extreme...
Geometrical approach in physical understanding of the Goos-Haenchen shift in one- And two-dimensional periodic structures
, Article Optics Letters ; Volume 33, Issue 24 , 2008 , Pages 2940-2942 ; 01469592 (ISSN) ; Naqavi, A ; Khavasi, A ; Mehrany, K ; Khorasani, S ; Rashidian, B ; Sharif University of Technology
Optical Society of America (OSA)
2008
Abstract
The Goos-Haenchen shift of a totally reflected beam at the planar interface of two dielectric media, as if the incident beam is reflected from beneath the interface between the incident and transmitted media, has been geometrically associated with the penetration of the incident photons in the less-dense forbidden transmission region. This geometrical approach is here generalized to analytically calculate the Goos-Haenchen shift in one- and two-dimensional periodic structures. Several numerical examples are presented, and the obtained results are successfully tested against the well-known Artman's formula. The proposed approach is shown to be a fast, simple, and efficient method that can...
Differential-transfer-matrix based on Airy's functions in analysis of planar optical structures with arbitrary index profiles
, Article IEEE Journal of Quantum Electronics ; Volume 44, Issue 4 , February , 2008 , Pages 324-330 ; 00189197 (ISSN) ; Sarrafi, P ; Mehrany, K ; Rashidian, B ; Sharif University of Technology
2008
Abstract
A novel analytical method for solution of planar optical structure with arbitrary refractive index profile is proposed. This new method is founded on differential-transfer-matrices, whose field solutions are based on Airy's trial functions. In contrast to conventional Wentzel, Kramers, and Brillouin (WKB) solutions, which diverge around the turning points, this approach can be successfully used for exact calculation of various functions, including eigenvalues of optical waveguides with arbitrary index profiles, and complex reflection and transmission coefficients, even at the presence of turning points. The method is rigorous and can be applied for both major polarizations. © 2008 IEEE
Oxygen sensing based on the oxidation process in resorufin dye
, Article Sensors and Actuators, B: Chemical ; Volume 122, Issue 1 , 2007 , Pages 109-117 ; 09254005 (ISSN) ; Razani, M ; Sharif University of Technology
2007
Abstract
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...