Sharif Digital Repository

A significant step in color image compression is to apply a color space transformation to the original RGB image to concentrate most of its energy in one plane. Standard JPEG-based compression methods utilize predefined transformations like RGB to YCbCr. In this paper, a devised algorithm is proposed to optimize the transformation for each image. The algorithm iteratively increases the energy concentration by optimizing a novel cost function while limiting the matrix determinant to a bounded region  

Color image segmentation is a primitive operation in many image processing and computer vision applications. Accordingly, there exist numerous segmentation approaches in the literature, which might be misleading for a researcher who is looking for a practical algorithm. While many researchers are still using the tools which belong to the old color space paradigm, there is evidence in the research established in the eighties that a proper descriptor of color vectors should act locally in the color domain. In this paper, these results are used to propose a new color image segmentation method. The proposed method searches for the principal colors, defined as the intersections of the cylindrical... 

In this paper, we have proposed a new face detection method which combines the AdaBoost algorithm with skin color information and support vector machine (SVM). First, a cascade classifier based on AdaBoost is used to detect faces in images. Due to noise and illumination changes some nonfaces might be detected too, therefore we have used a skin color model in the YCbCr color space to remove some of the detected nonfaces. Finally, we have utilized SVM to detect faces more accurately. Experimental results show that the performance of the proposed method is higher than the basic AdaBoost in the sense of detecting fewer nonfaces  

We revisit the classical edge coloring problem for general graphs in the streaming model. In this model, the input graph is presented as a stream of edges, and the algorithm must report colors assigned to the edges in a streaming fashion, using a memory of size O(n polylog n) on graphs of up to O(n2) edges. In ESA 2019 and SOSA 2021, two elegant randomized algorithms were presented for this problem in the adversarial edge arrival model, where the latest one colors any input graph using O(Δ2/s) colors with high probability in O (ns) space. In this short note, we propose two extremely simple streaming algorithms that achieve the same color and space bounds deterministically. Besides being... 

Scheduling sports leagues has drawn significant attention to itself in recent years, as it involves considerable revenue as well as challenging combinatorial optimization problems. A particular class of these problems is the Traveling Tournament Problem (TTP) which focuses on minimizing the total traveling distance for teams. In this paper, an efficient simulated annealing approach is presented for TTP which applies two simultaneous and disparate models for the problem in order to search the solutions space more effectively. Also, a computationally efficient modified greedy scheme is proposed for constructing a favorable initial solution for the simulated annealing algorithm. Our... 

Let G be a graph. The core of G, denoted by G Δ, is the subgraph of G induced by the vertices of degree Δ(G), where Δ(G) denotes the maximum degree of G. A k-edge coloring of G is a function f: E(G) → L such that |L| = k and f (e 1) ≠ f (e 2) for all two adjacent edges e 1 and e 2 of G. The chromatic index of G, denoted by χ′(G), is the minimum number k for which G has a k-edge coloring. A graph G is said to be Class 1 if χ′(G) = Δ(G) and Class 2 if χ′(G) = Δ(G) + 1. In this paper it is shown that every connected graph G of even order and with Δ(G Δ) ≤ 2 is Class 1 if |G Δ| ≤ 9 or G Δ is a cycle of order 10  

In this work, we study the problem of linear index coding from graph homomorphism point of view. We show that the decision version of linear (scalar or vector) index coding problem is equivalent to certain graph homomorphism problem. Using this equivalence expression, we conclude the following results. First we introduce new lower bounds on linear index of graphs. Next, we show that if the linear index of a graph over a finite filed is bounded by a constant, then by changing the ground field, the linear index of the graph may change by at most a constant factor that is independent from the size of the graph. Finally, we show that the decision version of linear index coding problem is... 

A graph G is called uniquelyk-list colorable (UkLC) if there exists a list of colors on its vertices, say L= { Sv∣ v∈ V(G) } , each of size k, such that there is a unique proper list coloring of G from this list of colors. A graph G is said to have propertyM(k) if it is not uniquely k-list colorable. Mahmoodian and Mahdian (Ars Comb 51:295–305, 1999) characterized all graphs with property M(2). For k≥ 3 property M(k) has been studied only for multipartite graphs. Here we find bounds on M(k) for graphs embedded on surfaces, and obtain new results on planar graphs. We begin a general study of bounds on M(k) for regular graphs, as well as for graphs with varying list sizes. © 2018, Springer... 

The coloring of hypergraph and its special case Steiner triple systems, STS(v), is studied extensively. But the defining set of the coloring of hypergraph even its special case STS(v), has not been explored yet. We study minimum defining set and the largest minimal defining set for 3-coloring of STS(v). We determined minimum defining set and the largest minimal defining set, for all non-isomorphic STS(v), v £ 15. Also we have found the defining number for all Steiner triple systems of order v, and some lower bounds for the size of the largest minimal defining set for all Steiner triple systems of order v, for each admissible v. © 2021 Taru Publications  

Background: Recently, concerns have been raised regarding the environmental and public health safety of azo dyes, the most widely used synthetic dyes. The membrane technique has been introduced as one of the efficient methods for dye removal treatments. Polyvinylidene fluoride (PVDF) membrane manipulated by surfactants was studied for removal of the azo dye, carmoisine. Methods: PVDF membrane was prepared via non-solvent-induced phase separation (NIPS) and used to remove the azo dye, carmoisine. Three nonionic surfactants including Tween 20, Tween 60, and Tween 80 were used individually as additives in casting solutions to improve PVDF membrane properties. Results: Fourier-transform infrared... 

By watermarking an image, we hide a pattern in it in such a way that the pattern is not visible but can be extracted using a decomposition algorithm and a key in the receiver side. The watermark pattern can be a character string or any small image (pattern). One of the main applications of watermarking is its application in proving digital image ownership in widely used Internet. In this paper, we present a watermarking method for color images which is robust with respect to usual attacks such as noise addition, smoothing, compression and also rotation. The validity of correctness of retrieved watermark is based on the result of a Naive-Bayes classifier. This classier was trained on a set of... 

In real soccer goal keeper has a completely different behavior that the players. Thus we designed our goal keeper with some basic ideas taken from real soccer, which is moving mainly in goal area and using arms to take the balls. Our goal keeper has a moving mechanism based on 8 motors which enables it to move forward/backward, straight left/right and rotate around its geometrical center, and a sliding arm which moves toward the direction of ball faster than the robot body. Using 3 CCD cameras in front and rear left and right provides the goal keeper with a view of about 210 degrees. © 2001 Springer-Verlag Berlin Heidelberg  

In the List Coloring problem, the input is a graph G and list of colors L: V(G) → N for each vertex v∈ V(G). The objective is to test the existence of a coloring λ: V(G) → N such that for each v∈ V(G), λ(v) ∈ L(v) and for each edge (u, v) ∈ E(G), λ(u) ≠ λ(v). Fiala et al. (TCS 2011) proved that List Coloring is W[1]-hard when parameterized by the vertex cover number of the input graph. Recently, Gutin et al. (STACS 2020, SIDMA 2021) designed an O∗(2 k) time randomized algorithm for List Coloring where k is the size of the given clique modulator of the input graph. Since List Coloring is W[1]-hard parameterized by the vertex cover number, List Coloring is W[1]-hard parameterized by the size... 

The coloring of hypergraph and its special case Steiner triple systems, STS(v), is studied extensively. But the defining set of the coloring of hypergraph even its special case STS(v), has not been explored yet. We study minimum defining set and the largest minimal defining set for 3-coloring of STS(v). We determined minimum defining set and the largest minimal defining set, for all non-isomorphic STS(v), v £ 15. Also we have found the defining number for all Steiner triple systems of order v, and some lower bounds for the size of the largest minimal defining set for all Steiner triple systems of order v, for each admissible v. © 2022 Taru Publications  

Let d (σ) stand for the defining number of the colouring σ. In this paper we consider dmin = minγ d (γ) and dmax = maxγ d (γ) for the onto χ-colourings γ of the circular complete graph Kn, d. In this regard we obtain a lower bound for dmin (Kn, d) and we also prove that this parameter is asymptotically equal to χ - 1. Also, we show that when χ ≥ 4 and s ≠ 0 then dmax (Kχ d - s, d) = χ + 2 s - 3, and, moreover, we prove an inequality relating this parameter to the circular chromatic number for any graph G. © 2006 Elsevier B.V. All rights reserved  

Suppose we have a family F of sets. For every S∈F, a set D⊆S is a defining set for (F,S) if S is the only element of F that contains D as a subset. This concept has been studied in numerous cases, such as vertex colorings, perfect matchings, dominating sets, block designs, geodetics, orientations, and Latin squares. In this paper, first, we propose the concept of a defining set of a logical formula, and we prove that the computational complexity of such a problem is Σ2-complete. We also show that the computational complexity of the following problem about the defining set of vertex colorings of graphs is Σ2-complete: INSTANCE: A graph G with a vertex coloring c and an integer k.QUESTION: If...