Sharif Digital Repository

Hybrid electric vehicles (HEVs) have been developed as a promising way to decrease the fuel consumption and emissions of conventional vehicles. Although the noise emission of HEVs is generally lower than that of conventional vehicles, it is still an issue, especially in urban transportation. In this paper, a power management strategy is developed to minimize the annoying noise of the engine for an HEV. This is a modified version of the strategy that was originally established based on the speed ratio of continuously variable transmission (CVT) as the control parameter (CVT-based strategy). The engine combustion noise is assessed using the experimental data of the in-cylinder pressure. Also,... 

One way to reduce vehicles' fuel consumption (FC) is to optimize different parts of its powertrain. Among different modern powertrains, continuously variable transmission (CVT) is one of the common types which changes speed ratio between engine and wheels, continuously. Therefore, the CVT allows the engine to operate at its fuel-optimal speed. Due to the limited power transmission capacity and speed ratio range of the CVT, researchers attempted to combine the CVT with a planetary gear train and a fixed ratio mechanism. This mechanism is called infinitely variable transmission (IVT). In this study, a multi-speed gearbox (MSG) is used in the IVT and its impact on the powertrain performance and... 

A mixed graph is obtained from a graph by orienting some of its edges. The Hermitian adjacency matrix of a mixed graph with the vertex set {v1,…,vn}, is the matrix H=[hij]n×n, where hij=−hji=i if there is a directed edge from vi to vj, hij=1 if there exists an undirected edge between vi and vj, and hij=0 otherwise. The Hermitian spectrum of a mixed graph is defined to be the spectrum of its Hermitian adjacency matrix. In this paper we study mixed graphs which are determined by their Hermitian spectrum (DHS). First, we show that each mixed cycle is switching equivalent to either a mixed cycle with no directed edges (Cn), a mixed cycle with exactly one directed edge (Cn 1), or a mixed cycle... 

Let G be a graph. The chromatic edge-stability number esχ(G) of a graph G is the minimum number of edges of G whose removal results in a graph H with χ(H)=χ(G)−1. A Nordhaus–Gaddum type inequality for the chromatic edge-stability number is proved. Sharp upper bounds on esχ are given for general graphs in terms of size and of maximum degree, respectively. All bounds are demonstrated to be sharp. Graphs with esχ=1 are considered and in particular characterized among k-regular graphs for k≤5. Several open problems are also stated. © 2019 Elsevier Ltd  

A weighted graph Gω consists of a simple graph G with a weight ω, which is a mapping, ω: E(G)→Z∖{0}. A signed graph is a graph whose edges are labelled with −1 or 1. In this paper, we characterize graphs which have a sign such that their signed adjacency matrix has full rank, and graphs which have a weight such that their weighted adjacency matrix does not have full rank. We show that for any arbitrary simple graph G, there is a sign σ so that Gσ has full rank if and only if G has a {1,2}-factor. We also show that for a graph G, there is a weight ω so that Gω does not have full rank if and only if G has at least two {1,2}-factors. © 2020 Elsevier B.V  

Service oriented architecture is based on the provision of services. To enhance the performance of the systems by providing a better combination of services, it is necessary to extract more information compared to the one in the service registry. In this regard, the accomplished works have been focusing on the basic concepts of service-oriented architecture. The service composition is based on the information in service registry, provided by the service provider. Further, centralized combination with insufficient information does not meet the system performance requirements. This solution helps to facilitate resource distribution and reduces tasks of the central unit. In this paper, efforts... 

Nowadays computational complexity of fast Walsh Hadamard transform and non-linearity for Boolean functions and large cryptographic substitution boxes is a major challenge of modern cryptography research on strengthening encryption schemes against linear and differential attacks. Time and memory complexities of the best existing algorithm for computing fast Walsh Hadamard transform and non-linearity for (Formula presented.) substitution boxes is (Formula presented.). This paper proposes three new innovation in acceleration methods that improve the computation time for paralleled Walsh matrix up to 68 folds and the evaluation time for non-linearity degree up to 1021 folds. These methods... 

In this paper, we study graphs whose matching polynomials have only integer zeros. A graph is matching integral if the zeros of its matching polynomial are all integers. We characterize all matching integral traceable graphs. We show that apart from K7(set minus)(E(C3)∪E(C4)) there is no connected k-regular matching integral graph if k≥2. It is also shown that if G is a graph with a perfect matching, then its matching polynomial has a zero in the interval (0,1]. Finally, we describe all claw-free matching integral graphs  

In this paper, we study graphs whose matching polynomials have only integer zeros. A graph is matching integral if the zeros of its matching polynomial are all integers. We characterize all matching integral traceable graphs. We show that apart from K7∖(E(C3)∪E(C4)) there is no connected k-regular matching integral graph if k≥2. It is also shown that if G is a graph with a perfect matching, then its matching polynomial has a zero in the interval (0,1]. Finally, we describe all claw-free matching integral graphs. © 2017 Elsevier B.V  

As a country's financing arm, the capital market can play a crucial role in long-term projects and be responsible for large-scale financing. While the development of rail transport has exceptionally positive and significant effects on the country's macroeconomy, and investment in this sector leads to the prosperity of other economic sectors, the return on investment may be delayed or unclear. Consequently, this uncertainty diminishes the investment appeal in this field. Thus, predicting the price and future value of railway company stocks on the stock market is vital due to the need for the foresight to take safe investment measures and achieve sustainable financing. To this end, this paper... 

We investigate how the inverse degree index of graphs depends on their cyclomatic number. In particular, we provide sharp lower bounds on the inverse degree index over all graphs on a given number of vertices with a given cyclomatic number. We also deduce some structural properties of extremal graphs. Some open questions regarding the upper bound over the same class of graphs are discussed and some possible further developments are indicated. © 2023, University of Nis. All rights reserved  

In this investigation, a mathematical model for HDS of diesel fuel in a slurry bubble column reactor was developed. The model is based on the axial dispersion of the heterogeneous gas flow regime, which includes two various bubble classes: large (20±70mm) and small (1±10mm). By assuming only large or large plus small bubbles in the column, single- and two-bubble class mode equations are developed. The developed models to solving the mass and enthalpy balances from which the sulfur conversion was obtained that undertaken. The chemical kinetics over NiMoS/γ-Al2O3 catalyst were undertaken for the reaction rate of the involved reactions. The reactor operating conditions... 

In industry, utilizing membrane separation technology to purify natural gas streams is of remarkable significance. Molecular Simulation was used in the current article to study the structural and gas separation properties of polydimethylsiloxane (PDMS)/zeolite 4A Mixed Matrix Membranes (MMMs). To explore the optimal performance of MMMs, several structural analyses, namely Fractional Free Volume (FFV), Radial Distribution Function (RDF), X-Ray Diffraction (XRD) and also Glass Transition Temperature (Tg) as one of the most important properties of membranes have been evaluated. Also, the solubilities and diffusivities of periodic cells were respectively measured using MSD and adsorption... 

In a gas transmission network (GTN), faults can easily propagate due to the interconnections of streams. The main objective of this paper is to develop a systematic framework for an online decision support system (DSS) in order to make the right decisions to get the GTN out of critical conditions (which cannot be handled by the plant controllers) smoothly. One of the key features of the proposed scheme is its lack of dependence on prior knowledge of the fault signals (e.g., number of faults, and their origin). In this article, the GTN is modeled by a fuzzy directed graph (FDG). The proposed approach utilizes a reasoning algorithm based on the deviations that exist in the process variables... 

Due to the increasing number of people suffering from physical disabilities in the elbow and wrist, developing an assistive wearable robot seems crucial. These disabilities are mostly common in elderly people and people who are suffering from spinal injury or stroke. In this paper, a wearable assistive robot for rehabilitation of the wrist and elbow is developed. The mechanism has 3 Degree of Freedom (DoF); two active DoF for assisting the exion/extension of the elbow and wrist, and a passive one in order to have unconstrained supination/pronation of the forearm. The motors and sensors were chosen based on kinematic constraints governing the motion of arms and wrists. Finally, with the...