Sharif Digital Repository

Liu and Xu (1998) and Ellingham, Nam and Voss (2002) independently showed that every k-edge-connected simple graph G has a spanning tree T such that for each vertex v, dT(v) ≤ ⌈ d(v)/k ⌉ + 2. In this paper we show that every k-edge-connected graph G has a spanning tree T such that for each vertex v, dT(v)≤ ⌈ d(v)-2/k ⌉ + 2; also if G has k edge-disjoint spanning trees, then T can be found such that for each vertex v, dT(v) ≤ ⌈ d(v)-1/k ⌉ + 1. This result implies that every (r-1)-edge-connected r-regular graph (with r ≥ 4) has a spanning Eulerian subgraph whose degrees lie in the set {2,4,6}; also reduces the edge-connectivity needed for some theorems due to Barát and Gerbner (2014) and... 

Let G be a graph and let f be a positive integer-valued function on V(G). In this paper, we show that if for all S⊆V(G), ω(G∖S)<∑v∈S(f(v)−2)+2+ω(G[S]), then G has a spanning tree T containing an arbitrary given matching such that for each vertex v, dT(v)≤f(v), where ω(G∖S) denotes the number of components of G∖S and ω(G[S]) denotes the number of components of the induced subgraph G[S] with the vertex set S. This is an improvement of several results. Next, we prove that if for all S⊆V(G), ω(G∖S)≤∑v∈S(f(v)−1)+1, then G admits a spanning closed walk passing through the edges of an arbitrary given matching meeting each vertex v at most f(v) times. This result solves a long-standing conjecture... 

In this paper, we show that every (3k−3)-edge-connected graph G, under a certain degree condition, can be edge-decomposed into k factors G1,…,Gk such that for each vertex v∈V(Gi), |dGi(v)−dG(v)/k|<1, where 1≤i≤k. As an application, we deduce that every 6-edge-connected graph G can be edge-decomposed into three factors G1, G2, and G3 such that for each vertex v∈V(Gi) with 1≤i≤3, |dGi(v)−dG(v)/3|<1, unless G has exactly one vertex z with dG(z)⁄≡30. Next, we show that every odd-(3k−2)-edge-connected graph G can be edge-decomposed into k factors G1,…,Gk such that for each vertex v∈V(Gi), dGi(v) and dG(v) have the same parity and |dGi(v)−dG(v)/k|<2, where k is an odd positive integer and 1≤i≤k.... 

In 2006 Barát and Thomassen conjectured that every planar 4-edge-connected 4-regular simple graph of size divisible by three admits a claw-decomposition. Later, Lai (2007) disproved this conjecture by a family of planar graphs with edge-connectivity 4 which the smallest one contains 24 vertices. In this note, we first give a smaller counterexample having only 18 vertices and next construct a family of planar 4-connected essentially 6-edge-connected 4-regular simple graphs of size divisible by three with no claw-decompositions. This result provides the sharpness for two known results which say that every 5-edge-connected graph of size divisible by three admits a claw-decomposition if it is... 

Let G be a graph, let k be a positive integer, and let p:V(G)→{−1,…,k−2} be a mapping with |E(G)|≡k∑v∈V(G)p(v). In this paper, we show that if G is essentially (3k−3)-edge-connected and for each vertex v, dG(v)≥2k−1+p(v), then G has an orientation such that for each vertex v, dG+(v)≡kp(v), and [Formula presented] In addition, we show that if G can be decomposed into 2k−2 edge-disjoint spanning trees and a factor F having an orientation such that for each vertex v, dF+(v)≥l0(v), then G has an orientation such that for each vertex v, dG+(v)≡kp(v), and s(v)≤dG+(v)≤dG(v)−s0(v), where s, s0, and l0 are three integer-valued functions on V(G) satisfying s(v)+s0(v)+k−1≤dG(v) and... 

Underwater gliders (UGs) are used for seabed data collection due to their low power consumption, which is an advantage for extending endurance in deep seas. The geometrical characteristics directly affect the stability and performance of these types of robots in terms of their endurance. This study aimed to determine the effect of the body length-to-diameter ratio on maneuverability during zigzag and helical maneuvers. For this, the theoretically derived formulas based on non-linear hydrodynamic coefficients for the body and wing have been described in six degrees of freedom (six-DOF). The model and theoretical formulas have been validated by experimental tests on the Sharif University of... 

Nowadays, underwater gliders (UGs) are known as efficiency vehicles to observe and quantify water properties concerning marine environments, seabed characteristics, and water depths. The development of appropriate dynamic and state space models is necessary for designing an effective control system. This study aims to develop state space models for UGs equipped with embedded actuators based on a non-linear dynamic model that takes into account the hydrodynamic characteristics of the body and wings. The method involves utilizing sensitivity analysis and assumptions to construct two distinct state space models, along with the linearization of the non-linear model in horizontal and vertical... 

Online intelligent knowledge extraction from real-world nonstationary data streams presents a multiobjective optimization challenge. Here, we characterize the learning process on a trajectory of global optimality to simultaneously satisfy six high-profile objectives: 1) optimum generalization for the best bias-variance tradeoff; 2) compactness of knowledgebase; 3) memory retention and stability-plasticity balance; 4) universality and full autonomy; 5) robustness against outliers, noise, and model uncertainty; and 6) active concept drift detection and adaptation. We propose a flexible Takagi-Sugeno (TS) fuzzy system, named UFAREX, that self-constructs and self-guards from scratch in a... 

Harnessing natural water currents for renewable energy generation holds significant promise. Flapping foil hydrokinetic turbines (FHTs), inspired by aquatic organisms' propulsion mechanisms, leverage undulating motion to extract energy from flowing water. This study investigates the impact of hydrofoil shape and mechanical parameters on oscillating tandem hydrofoil systems' performance for energy harvesting, focusing on Persian Gulf tidal currents. Computational Fluid Dynamics (CFD) in a 2D domain is employed for analysis. Parameters include hydrofoil profiles (IFS, NACA 0015, HSVA, and flat plate), damping coefficient, and initial pitch angle optimized for low-level currents around 1 m/s,... 

Local educational institutions produce in-house English for Specific Purpose (ESP) materials according to the curriculum policies designated and developed by the Ministry of Higher Education In Iran. To this end, this book aims to be used in the Iranian setting at the tertiary level for undergraduate students majoring in Mechanical Engineering. Moreover, the style of English usage in this ESP textbook is American.
Regarding the content of the textbook, it has both thematic organizations in which the topics are relevant and includes sufficient treatment of the target language areas necessary for the students. The principle organizing approach of this textbook is theme-based. In addition,... 

The aim of this study is to employ feedback control loops to provide a stable forward dynamics simulation of human movement under repeated position constraint conditions in the environment, particularly during stair climbing. A ten-degrees-of-freedom skeletal model containing 18 Hill-type musculotendon actuators per leg was employed to simulate the model in the sagittal plane. The postural tracking and obstacle avoidance were provided by the proportional—integral—derivative controller according to the modulation of the time rate change of the joint kinematics. The stability of the model was maintained by controlling the velocity of the body's centre of mass according to the desired centre of... 

A combination of silica chloride and wet SiO2 was used as an effective deacetalizating agent for the conversion of acetals to their corresponding carbonyl derivatives under mild and heterogeneous condition  

Free Content Selective synthesis of conjugated enynes from α-arylalkynols using LiCl-Acidic Al2O3 under solvent-free conditions  

7H-benzimidazo[2,1-a]benz[de]isoquinolin-7-one compounds were prepared in a selective manner by reaction between o-phenylenediamines and appropriate 1,8-naphthalenedicarboxylic anhydrides using acidic alumina under microwave irradiation