Sharif Digital Repository

Many Middle-East countries, like Iran, have dynamic banking industries and have observed merger and acquisitions (M&A) waves. M&A waves are usually defined in the developed world context and some of their main drivers were identified as: market timing, environment's shocks, merger manias, government regulation and regulatory, and technological changes. It has been discussed that merger waves and their reasons are among the ten most important unsolved mysteries in the field of finance (Brealey and Myers, 1991, p. 923), and as a result of this, it was not possible to completely clarify the reasons behind emerging M&A waves, especially in developing countries; for this reason in these... 

This chapter aims at pointing out that how mergers and acquisitions (M&As) as popular strategies which they are based on external growth approach have affected the performance of banks and entrepreneurial orientation (EO) in the context of Iranian financial sector. In this regard, it has been tried to investigate in what way EO moderates the relationships between the performance of banks in one hand, and M&As on the other hand. For this goal, 114 participants including the top and middle managers of the Iranian banks were chosen to be closely considered. The research is an applied research and a cross-correlation methodology has been used to spotlight on the probable relationships between EO... 

A new Zinc phosphating bath, which produces coatings at relatively lower temperatures within a reasonable time by using of chemical accelerators has been devised. Improvement of the bath performance by the addition of divalent cations like calcium, nickel has been studied. Bath formulation and operating conditions have been optimized by coating weight determinations. Stable samples of phosphating formulations with and without calcium and nickel salts were prepared and the structure and morphology of the phosphate coatings were determined by using X-ray diffraction (XRD) techniques, scanning electron microscopy. ASTMB117 salt spray test and electrochemical impedance spectroscopy (EIS) were... 

In a recently published article by Backer [Opt. Express 27(21), 30308 (2019).], a computational inverse design method is developed for designing optical systems composed of multiple metasurfaces. The forward propagation model used in this method was a discretized version of the angular spectrum propagator described by Goodman [Introduction to Fourier Optics, 1996]. However, slight modifications are necessary to increase the accuracy of this inverse design method. This comment examines the accuracy of the results obtained by the above-mentioned method by a full-wave electromagnetic solver and explains the reason of their difference. Thereafter, slight modifications to the method proposed by... 

In the Touring Polygons Problem (TPP) there is a start point s, a sequence of simple polygons P = (P1,...,Pk) and a target point t in the plane. The goal is to obtain a path of minimum possible length that starts from s, visits in order each of the polygons in P and ends at t. This problem has a polynomial time algorithm when the polygons in P are convex and is NP-hard in general case. But, it has been open whether the problem is NP-hard when the polygons are pairwise disjoint. In this paper, we prove that TPP is also NP-hard when the polygons are pairwise disjoint in any Lp norm even if each polygon consists of at most two line segments. This result solves an open problem from STOC '03 and... 

In the Touring Polygons Problem (TPP) there is a start point s, a sequence of simple polygons P=(P1,. . .,Pk) and a target point t in the plane. The goal is to obtain a path of minimum possible length that starts from s, visits in order each of the polygons in P and ends at t. This problem was introduced by Dror, Efrat, Lubiw and Mitchell in STOC '03. They proposed a polynomial time algorithm for the problem when the polygons in P are convex and proved its NP-hardness for intersecting and non-convex polygons. They asked as an open problem whether TPP is NP-hard when the polygons are pairwise disjoint. In this paper, we prove that TPP is also NP-hard when the polygons are pairwise disjoint in... 

In the touring polygons problem (TPP), for a given sequence (s= P0, P1, ⋯, Pk, t = Pk+1) of polygons in the plane, where s and t are two points, the goal is to find a shortest path that starts from s, visits each of the polygons in order and ends at t. In the constrained version of TPP, there is another sequence (F0, ⋯, Fk) of polygons called fences, and the portion of the path from Pi to Pi+1 must lie inside the fence Fi. TPP is NP-hard for disjoint non-convex polygons, while TPP and constrained TPP are polynomially solvable when the polygons are convex and the fences are simple polygons. In this work, we present the first polynomial time algorithm for solving constrained TPP when the... 

In this paper, we consider the restricted version of the well-known 2D line simplification problem under area measures and for restricted version. We first propose a unified definition for both of sum-area and difference-area measures that can be used on a general path of n vertices. The optimal simplification runs in O(n 3) under both of these measures. Under sum-area measure and for a realistic input path, we propose an approximation algorithm of O n2 time complexity to find a simplification of the input path, where is the absolute error of this algorithm compared to the optimal solution. Furthermore, for difference-area measure, we present an algorithm that finds the optimal... 

A Triangulated Irregular Network (TIN) is a data structure that is usually used for representing and storing monotone geographic surfaces, approximately. In this representation, the surface is approximated by a set of triangular faces whose projection on the XY-plane is a triangulation. The visibility graph of a TIN is a graph whose vertices correspond to the vertices of the TIN and there is an edge between two vertices if their corresponding vertices on TIN see each other, i.e. the segment that connects these vertices completely lies above the TIN. Computing the visibility graph of a TIN and its properties have been considered thoroughly in the literature. In this paper, we consider this... 

Due to the limitations of two-dimensional models in mimicking intratumoral drug delivery, three-dimensional tumor spheroid-on-chip models have been considered recently. Even though various models have been proposed in this field, many unknowns still exist about their reliability in imitating in vivo conditions. In addition, most of these models neglect the replication of drug transport from the bloodstream. In the current research, considering the interface of tumor and blood vessels, new designs of microfluidic devices are developed to resemble the in vivo conditions more closely. Then, drug transport in the proposed models is studied numerically using porous media theory under dynamic... 

We construct a new proximity graph, called the Pie Delaunay graph, on a set of n points which is a super graph of Yao graph and Euclidean minimum spanning tree (EMST). We efficiently maintain the Pie Delaunay graph where the points are moving in the plane. We use the kinetic Pie Delaunay graph to create a kinetic data structure (KDS) for maintenance of the Yao graph and the EMST on a set of n moving points in 2-dimensional space. Assuming x and y coordinates of the points are defined by algebraic functions of at most degree s, the structure uses O(n) space, O(nlogn) preprocessing time, and processes O(n 2 λ 2s∈+∈2(n)β s + 2(n)) events for the Yao graph and O(n 2 λ 2s + 2(n)) events for the... 

An integrated photonic neural network is proposed based on on-chip cascaded one-dimensional (1D) metasurfaces. High-contrast transmitarray metasurfaces, termed as metalines in this paper, are defined sequentially in the silicon-on-insulator substrate with a distance much larger than the operation wavelength. Matrix-vector multiplications can be accomplished in parallel and with low energy consumption due to intrinsic parallelism and low-loss of silicon metalines. The proposed on-chip whole-passive fully-optical meta-neural-network is very compact and works at the speed of light, with very low energy consumption. Various complex functions that are performed by digital neural networks can be... 

For a set of n disjoint line segments S in R2, the visibility testing problem (VTP) is to test whether the query point p sees a query segment s∈S. For this configuration, the visibility counting problem (VCP) is to preprocess S such that the number of visible segments in S from any query point p can be computed quickly. In this paper, we solve VTP in expected logarithmic query time using quadratic preprocessing time and space. Moreover, we propose a (1+δ)-approximation algorithm for VCP using at most quadratic preprocessing time and space. The query time of this method is Oε (1/δ 2√n) where Oε (f(n))=O(f(n)nε) and ε>0 is an arbitrary constant number  

Due to the technical advances in power electronic industry, employing inverter-based distributed energy resources (IBDERs) are increased in electric power systems. Distributed generators (DGs) with the rating capacity of few megawatts are commonly connected to the distribution level of power systems which are inherently unbalanced. A cluster of IBDERs and loads form a small-scale grid called microgrid (MG) which can operate independent of the main grid. In a MG, grid forming voltage source converters (VSCs) are used to control the voltages and frequency of the MG. However, grid forming VSCs with conventional control schemes cannot do this task properly when the MG is unbalanced. In this... 

A study of thick-walled spherical vessels under steady-state radial temperature gradients using elasto-plastic analysis is reported. By considering a maximum plastic radius and using the thermal autofrettage method for the strengthening mechanism, the optimum wall thickness of the vessel for a given temperature gradient across the vessel is obtained. Finally, in the case of thermal loading on a vessel, the effect of convective heat transfer on the optimum thickness is considered, and a general formula for the optimum thickness and design graphs for several different cases are presented. © 2004 Elsevier Ltd. All rights reserved  

Photonic integrated circuits (PICs) with rapid programming capability are highly desirable to realize flexible photonic networks. Phase change technology offers nonvolatile programmability in PICs. Here, an alternate way of controlling the light flow to interferometers, directional couplers, and phase shifters in the photonic integrated circuits, that is on-chip programmable metasurfaces is reported. Compact and low-loss on-chip metasurfaces can be demonstrated on a Sb2Se3 thin film using direct laser writing. On-chip focusing and splitting are realized with a single layer of the on-chip metasurface. Also, a more complex machine learning task of pattern recognition is accomplished by a... 

The proof of concept of a polarization-sensitive temperature sensor composed of a silicon Fabry–Perot resonator sandwiched between double-layered subwavelength metallic slit arrays is presented at the operation wavelength of 1.55 µm. Temperature variations can be monitored by measuring the changes in reflection intensity, which is mainly induced by the thermo-optic effect and thermal expansion effect of silicon. For TM-polarized electromagnetic illumination (magnetic field parallel to the slits), the reflection properties of the proposed sensor can be adjusted by proper design of the subwavelength metallic slit arrays’ parameters, such as periodicity, metal film thickness, and slit width.... 

For a set of n points in the plane, this paper presents simple kinetic data structures (KDSs) for solutions to some fundamental proximity problems, namely, the all nearest neighbors problem, the closest pair problem, and the Euclidean minimum spanning tree (EMST) problem. Also, the paper introduces KDSs for maintenance of two well-studied sparse proximity graphs, the Yao graph and the Semi-Yao graph. We use sparse graph representations, the Pie Delaunay graph and the Equilateral Delaunay graph, to provide new solutions for the proximity problems. Then we design KDSs that efficiently maintain these sparse graphs on a set of n moving points, where the trajectory of each point is assumed to be... 

Medium power distributed energy resources (DERs) are commonly connected to medium voltage distribution systems via voltage source converters (VSCs). Several guidelines and standards have been developed to establish the needed criteria and requirements for DERs interconnections. In this respect, it is preferred to reinforce the VSC fault ride through (FRT) capability, which considerably minimizes the DG outage period and reconnection time and results in a resilient system against short circuits. Considering the significant number of asymmetrical faults in distribution systems, the VSC response in such conditions must be investigated, and consequently, its FRT capability must be reinforced. In... 

Dynamic hydrosalinity models are available, but are not used extensively on a large scale soil which receives wastewater from industrial areas, partly because adequate database are expensive to be obtained. Thus, for this reason, there is an urgent need to assess the salt and other pollutant loads collected in wastewater flows into the soil and/ or ground water systems. A conceptual hydrosalinity model was used on two major underlying principals of mass balance and steady state. This model was initially tested on the 4,117 km2 plains west of the Yazd-Ardakan district in the central part of Iran. This model was used at a time when the soil and ground water salinity problem was serious due to...