Sharif Digital Repository

Let G be a graph on n vertices with r := [n/2] and let γ 1 ≥ · · · ≥ γ n be adjacency eigenvalues of G. Then the Ḧuckel energy of G, HE(G), is defined as [Equation presented] The concept of Hückel energy was introduced by Coulson as it gives a good approximation for the π-electron energy of molecular graphs. We obtain two upper bounds and a lower bound for HE(G). When n is even, it is shown that equality holds in both upper bounds if and only if G is a strongly regular graph with parameters (n, k, γ, μ) = (4t2 + 4t + 2, 2t2 + 3t + 1, t2 + 2t, t2 + 2t + 1), for positive integer t. Furthermore, we will give an infinite family of these strongly regular graph whose construction was communicated... 

Considering the interaction of flexural moment and shear force in the steel frames with haunch or intermediate beam length and eccentrically braced frames with intermediate link length is a major concern of the structural analysis and design. This article contains two stages. In the first stage, to investigate the moment–shear interaction for the highly ductile steel I-sections, a study is carried out using finite element analysis and a simple and practical relationship is developed. In the second stage, a simple approach based on virtual work method for assemblage of interconnected rigid bodies is employed to consider collapse mechanisms with mixed hinges. Using this approach, the... 

Considering the interaction of flexural moment and shear force in the steel frames with haunch or intermediate beam length and eccentrically braced frames with intermediate link length is a major concern of the structural analysis and design. This article contains two stages. In the first stage, to investigate the moment–shear interaction for the highly ductile steel I-sections, a study is carried out using finite element analysis and a simple and practical relationship is developed. In the second stage, a simple approach based on virtual work method for assemblage of interconnected rigid bodies is employed to consider collapse mechanisms with mixed hinges. Using this approach, the... 

Hydroxyapatite (HA) coatings were deposited on commercially pure titanium plates using a hydrothermal-electrochemical deposition method in an electrolyte containing calcium and phosphate ions. The deposition conditions used in this study were the followings: electrolyte temperature (33-80 °C), current density (1-8 mA/cm2), and deposition time (10-120 min). Needle-like and granular crystals of apatite coating were created with different concentrations of calcium (0.0021-0.042 M) and phosphate (0.00125-0.025 M) salts. The size of HA crystals of the coating was considerably changed with different concentration of calcium and phosphate salts, temperature of the electrolyte, and deposition time.... 

The floating photovoltaic (FPV) array, which consists of tens or hundreds of rows of floating photovoltaic systems, exhibits great economic and environmental benefits. An FPV array arranged in the ocean will be subjected to the combined action of wind, waves, and currents during the installation, service, and maintenance processes; however, systematic research in this field is still lacking. As a representative of the FPV array, this study on the hydrodynamic characteristics of a single-row FPV system is a fundamental prerequisite for the safe design of large-scale FPV arrays in the near future. In this paper, based on the potential theory, a numerical model of a single-row FPV system with... 

In this paper, the performance of some popular direct interconnection networks, namely the mesh, torus and hypercube, are studied with adaptive wormhole routing for different traffic patterns. We investigate the effect of the number of virtual channels and depth of their buffers on the performance of such strictly orthogonal topologies under uniform, hot-spot and matrix-transpose traffic patterns for generated messages, while the total buffer size associated to each physical channel is kept constant. In addition we analyze the effect of escape channel buffer length on the performance of a fully adaptive routing algorithm. It is shown that the optimal number of virtual channels and buffer... 

Dye-sensitized upconversion nanoparticles (UCNPs) have gained significant interest in biological applications. However, previous attempts to utilize these dye-sensitized UCNPs in the aqueous environment suffer from dramatic decline in the upconversion luminescence (UCL) intensity and problems with nanoparticles aggregation and water quenching. By employing indocyanine green (ICG) as a hydrophobic amplifier and energy harvester for UCNPs, we use a general, facile, and kinetically controlled mixing technology—flash nanoprecipitation (FNP)—to prepare aqueous stable ICG-sensitized UCNPs encapsulated by a biocompatible block copolymer poly (ethylene glycol)-b-poly (lactic-co-glycolic acid... 

We propose GraphOS, a system that allows a client that owns a graph database to outsource it to an untrusted server for storage and querying. It relies on doubly-oblivious primitives and trusted hardware to achieve a very strong privacy and efficiency notion which we call oblivious graph processing: the server learns nothing besides the number of graph vertexes and edges, and for each query its type and response size. At a technical level, GraphOS stores the graph on a doubly-oblivious data structure, so that all vertex/edge accesses are indistinguishable. For this purpose, we propose Omix++, a novel doubly-oblivious map that outperforms the previous state of the art by up to 34×, and may be... 

As the increasing demands of military detection, wireless communication and remote sensing make the spectrum even more crowded, radar sequence design meeting spectral compatibility requirement is a challenging and urgent problem. This study is devoted to designing optimised phase-coded sequences which keep spectral-compatible with the overlaid electromagnetic radiators and at the same time optimise the signal-to-interference-plus-noise ratio (SINR). First, an intelligent dynamic spectrum information around the radar system is achieved by a radio environmental map. The information is introduced to form a constrained optimisation process aimed at improving the spectral compatibility and the... 

Because of the compatibility with tandem devices and the ability to be manufactured at low temperatures, inverted perovskite solar cells have generated far-ranging interest for potential commercial applications. However, their efficiency remains inadequate owing to various traps in the perovskite film and the restricted hole blocking ability of the electron transport layer. Thus, in this work, a wide-bandgap n-type semiconductor, 4,6-bis(3,5-di(pyridin-4-yl)phenyl)-2-phenylpyrimidine (B4PyPPM), to modify a perovskite film via an anti-solvent method is introduced. The nitrogen sites of pyrimidine and pyridine rings in B4PyPPM exhibit strong interactions with the undercoordinated lead ions in... 

To study the mechanism of tsunami wave forces on round-ended piers and the force calculation method, a series of round-ended piers with different ratios of length to width (L/D, D is the diameter of the semicircle at both ends, L is the rectangular length between two end semicircles) are taken as the research object of this study. Firstly, a series of tsunami waves are experimentally generated over dry-bed and wet-beds with different water depths in a dam-break flume. Secondly, the pressure time histories on the outer sides of the round-ended piers are presented and explored. After that, the characteristics of the resultant force and moment at the pier bottom, the maximum force and moment as... 

In this paper, the parallel implementations of different iterative polynomial root finding methods on a processor with SIMD processing capability are reported. These methods are based on the construction of a sequence of approximations that converge to the set of roots. We have chosen four widely used methods namely Newton's, Durand-Kerner's, Aberth-Ehrlich's, and QD and implemented them using the SIMD instruction set of the Pentium processor with C++ and assembly language. Experiments show that a speedup of 3 or higher can be achieved, depending on the order of polynomial, required accuracy, and the method employed. © 2005 IEEE  

Face inpainting, the technique of restoring missing or damaged regions in facial images, is pivotal for applications like face recognition in occluded scenarios and image analysis with poor-quality captures. This process not only needs to produce realistic visuals but also preserve individual identity characteristics. The aim of this paper is to inpaint a face given periocular region (eyes-to-face) through a proposed new Generative Adversarial Network (GAN)-based model called Eyes-to-Face Network (E2F-Net). The proposed approach extracts identity and non-identity features from the periocular region using two dedicated encoders have been used. The extracted features are then mapped to the... 

Sulfur-containing gaseous contaminant treatment is a key issue in the healthy and sustainable development of industry, especially SO2 and H2S occur with natural gas extraction and fossil fuel burning. Traditionally, the commercial method for H2S or SO2 requires numerous desiccants and enormous energy consumption. Encouragingly, electrochemical coupling system, which provide an efficient, sustainable, and economic pathway for sulfur-containing gaseous contaminants removal, can convert H2S and SO2 to recyclable substance in a moderate environment and simultaneously transfer the energy contained in them to other more valuable product. The current review discusses the mechanism and principle of... 

We consider a problem of localizing a temporal path signal that evolves over time on a graph. A path signal represents the trajectory of a moving agent on a graph in a series of consecutive time stamps. Through combining dynamic programing and graph partitioning, we propose a path-localization algorithm with significantly reduced computational complexity. To analyze the localization performance, we use two evaluation metrics to quantify the localization error: The Hamming distance and the destination's distance between the ground-truth path and the estimated path. In random geometric graphs, we provide a closed-form expression for the localization error bound, and a tradeoff between... 

Silica nanoparticles, which have a broad range of sizes and specific surface features, have been used in many industrial applications. This study was conducted to synthesize monodispersed silica nanoparticles directly from tetraethyl orthosilicate (TEOS) with an alkaline catalyst (NH3) based on the sol–gel process and the Stöber method. A central composite design (CCD) is used to build a second-order (quadratic) model for the response variables without requiring a complete threelevel factorial experiment. The process was then optimized to achieve the minimum particle size with the lowest concentration of TEOS. Dynamic light scattering and scanning electron microscopy were used to analyze the... 

Nickel oxide (NiOx) is a promising hole transport material in inverted organic-inorganic metal halide perovskite solar cells. However, its low intrinsic conductivity hinders its further improvement in device performance. Here, we employ a trimercapto-s-triazine trisodium salt (TTTS) as a chelating agent of Ni2+ in the NiOx layer to improve its conductivity. Due to the electron-deficient triazine ring, the TTTS complexes with Ni2+ in NiOx via a strong Ni2+-N coordination bond and increases the ratio of Ni3+:Ni2+. The increased Ni3+ concentration adjusts the band structure of NiOx, thus enhancing hole density and mobility, eventually improving the intrinsic conductivity of NiOx. As a result,... 

Pesticides are indispensable in agricultural development, but their effectiveness is often hindered by natural factors like rain-off and degradation. Herein, tebuconazole nanopesticides (TEB NPs) with leaf-adhesive, water-stable, and small-sized were successfully prepared by flash nanoprecipitation using the biodegradable polyethylene glycol-b-poly (lactic-co-glycolic acid) as a carrier. The nanopesticides could be efficiently deposited on plant leaves with uniform distribution and exhibited a 14° lower contact angle with foliage compared to commercial suspensions. The encapsulation of TEB within the polymer enhanced its resistance to photolysis, resulting in a 5-h extension of its... 

Electrochemical co-deposition approach was expanded to prepare composite bio-ceramic coating of hydroxyapatite (HA)/polyvinyl acetate on the surface of titanium. The role is to improve the bioactive and crystallization properties. The results of XRD, XPS, SEM and TEM characterization showed that by increasing amount of vinyl acetate in the composite bio-ceramic coating before and after immersing in the simulated body fluid (SBF), an oriented growth of HA planes on the (0 0 2) direction had been observed on titanium substrate. Also significant surface morphology changes were obtained  

The effect of moisture on Shengli lignite breakage behavior and energy efficiency was studied experimentally using a standard Hardgrove mill fitted with a wattmeter. The grinding process concerned both the inputs, namely the occurrence and content of water and instantaneous energy consumption and the outputs, size-reduction and product fineness. Results show that the energy-size reduction process for grinding lignite is markedly influenced by moisture occurrence and content. Removing surface moisture from 37.90% to 16.61% (the air-dried condition) resulted in a slight increase of input energy by 0.04 kWh.t−1 per 10 s. However, with further drying inherent moisture to 0%, the consumed energy...