Sharif Digital Repository

In this paper a new post fault operation strategy is proposed for modular multilevel converter (MMC). The conventional MMC fault tolerant operation methods use redundant cells in spinning or cold reserve schemes, however in this work the MMC fault tolerant operation is achieved without requiring any redundant cells. The introduced strategy modifies capacitors reference voltages and arms modulation reference waveforms in faulty leg of MMC while other legs operate normally. The applied technique leads to having some degree of overvoltage in faulty leg capacitors which could be neglected since the number of cells is high. Simple realization and significant economic savings would be attained as... 

Mobile and rapidly assembled structures play an important role in building temporary and semi-permanent accommodations and shelters in post-disaster management. One of the most efficient construction systems that can be used in rapidly assembled buildings is lightweight panelized systems. Use of rapidly assembled panelized systems is becoming very popular for cutting the construction time and transportation costs that make them suitable options for rapid assembly construction. In addition, when acoustic and thermal insulation of buildings is important, foam filled composite sandwich panels are an effective solution. Soft, semi-rigid and rigid Polyurethane (PU) foams, which are first... 

Rebeca is an actor-based language for modeling concurrent and distributed systems as a set of reactive objects which communicate via asynchronous message passing. Rebeca is extended to support synchronous communication, and at the same time components are introduced to encapsulate the tightly coupled reactive objects which may communicate by synchronous messages. This provide us a language for modeling globally asynchronous and locally synchronous systems. Components interact only by asynchronous messages. This feature and also the eventdriven nature of the computation are exploited to introduce a modular verification approach in order to overcome the state explosion problem in model... 

Actor-based modeling, with encapsulated active objects which communicate asynchronously, is generally recognized to be well-suited for representing concurrent and distributed systems. In this paper we discuss the actor-based language Rebeca which is based on a formal operational interpretation of the actor model. Its Java-like syntax and object-based style of modeling makes it easy to use for software engineers, and its independent objects as units of concurrency leads to natural abstraction techniques necessary for model checking. We present a front-end tool for translating Rebeca to the languages of existing model checkers in order to model check Rebeca models. Automated modular... 

In this study, two novel biomimetic modular peptide motifs based on the alpha-2 subunit of type IV collagen (CO4A2) were designed and immobilized on a graphene platform to imitate integrin and heparan sulfate- (HS-) binding proteins. The in silico study was used to design 9-mer K[KGDRGD]AG and 10-mer KK[SGDRGD]AG for testing designed Integrin-Binding Peptide (dIBP) and HS-Binding Peptide (dHBP). The virtual docking technique was used to optimize the peptide motifs and their relevant receptors. Molecular dynamic (MD) simulation was used to evaluate the stability of peptide-receptor complexes. The effect of the platform on the differentiation of human mesenchymal stem cells (hMSCs) to... 

In this paper a novel hybrid algorithm for compensating the distortion of any interpolation has been proposed. In this Hybrid method, a modular approach was incorporated in an iterative fashion. The proposed technique features an impressive improvement at reduced computational complexity. The authors also extend the scheme to 2-D signals and actual (real) images and find that the solution exhibits great potential. Both the simulation results and mathematical analysis confirm the superiority of the Hybrid model over competing methods and demonstrate its robustness against additive noise  

Many real-world networks have a modular structure, and their component may undergo random errors and/or intentional attacks. More devastating situations may happen if the network components have a limited load capacity; the errors and attacks may lead to a cascading component removal process, and consequently, the network may lose its desired performance. In this brief, we investigate the tolerance of cascading errors and attacks in modular small-world networks. This brief studies the size of the largest connected component of the networks when cascading errors or attacks occur. The robustness of the network is tested as a function of both the intermodular connection and intramodular... 

Aspect-Oriented Software Development (AOSD) concentrates on determination and modularization of orthogonal concerns that cut across system modules. An aspect-oriented extension framework helps transform existing methodologies into processes which support AOSD. The authors propose a framework for extending agile methodologies with AOSD features. The stages required for constructing the framework have been identified by scrutinizing existing aspect-oriented methodologies and practices in order to extract the AOSD-specific stages required in each phase of the agile development process. Analysis shows that a methodology extended through this framework can be superior in agility in comparison to... 

In this paper we extended a previously investigated modular method that is designed to compensate for interpolation distortions of one-dimensional signals, to two dimensions (2-D). Next the proposed 2-D modular technique was applied in an iterative fashion and was shown through both simulations and theoretical analyses to enhance the convergence of the iterative technique. In fact, with only a few modules we were able to achieve drastic improvements in signal reconstruction, and with a much less computational complexity. Moreover, both the simulations and the theoretical analysis confirmed the robustness of the proposed scheme against additive noise  

In this paper a new voltage measurement technique for modular multilevel converter (MMC) capacitors is proposed. While all the capacitors voltages should be known for closed loop control of MMCs, only the arms voltages are measured employing the proposed method. Therefore, the number of voltage sensors reduced dramatically to one per arm. The capacitors voltage quantities are updated continuously using the arms voltage and the switching signals. Although the proposed method precision is depended on the equality of the capacitors, presented investigations show that the steady state error and even transient error in capacitors voltage estimation is ignorable for the proper operation of the... 

This paper proposes a new fault detection method for the modular multilevel converter (MMC) semiconductor power switches. While in common MMCs, the modules capacitor voltages are measured directly for control purposes, in this paper voltage measurement point changes to module output terminal improving fault diagnosis ability. Based on this measurement reconfiguration, a novel fault detection algorithm is designed for MMCs semiconductor power switches. The open circuit and short circuit faultsare detected based on unconformity between modules output voltage and switching signals. Simulations results confirm accurate and fast operation of the proposed algorithm in faulty module diagnosis.... 

Let G be a graph whose each component has order at least 3. Let s: E(G) → Zk for some integer k≥ 2 be an improper edge coloring of G (where adjacent edges may be assigned the same color). If the induced vertex coloring c: V(G) → Zk defined by c(v)=∑e∈Evs(e)inZk, (where the indicated sum is computed in Zk and Ev denotes the set of all edges incident to v) results in a proper vertex coloring of G, then we refer to such a coloring as an improper twin k-edge coloring. The minimum k for which G has an improper twin k-edge coloring is called the improper twin chromatic index of G and is denoted by χit′(G). It is known that χit′(G)=χ(G), unless χ(G)≡2(mod4) and in this case χit′(G)∈{χ(G),χ(G)+1}.... 

We use the topological entanglement entropy (TEE) as an efficient tool to fully characterize the Abelian phase of a Z2 ×Z2 spin liquid emerging as the ground state of topological color code (TCC), which is a class of stabilizer states on the honeycomb lattice. We provide the fusion rules of the quasiparticle (QP) excitations of the model by introducing single- or two-body operators on physical spins for each fusion process which justify the corresponding fusion outcome. Besides this, we extract the TEE from Renyi entanglement entropy (EE) of the TCC, analytically and numerically by finite size exact diagonalization on the disk shape regions with contractible boundaries. We obtain that the EE... 

Let p be a prime not dividing the integer n. By an Ihara result, we mean existence of a cokernel torsion-free injection from a full lattice in the space of p-old modular forms into a full lattice in the space of all modular forms of level pn. In this paper, we will prove an Ihara result in the number field case, for Siegel modular forms. The case of elliptic modular forms is discussed in Ihara (Discrete subgroups of Lie groups and applications to moduli, Oxford University Press, Bombay, 1975). We will use a geometric formulation for the notion of p-old Siegel modular forms (Rastegar in BIMS 43(7):1–23, 2017). Then, we apply an argument by Pappas, and prove the Ihara result using density of... 

In the IEEE 802.1D standard for the Media Access Control layer (MAC layer) bridges, there is an STP (Spanning Tree Protocol) definition, based on the algorithm that was proposed by Radia Perlman. In this paper, we give a formal proof for correctness of the STP algorithm by showing that finally a single node is selected as the root of the tree and the loops are eliminated correctly. We use formal inductive reasoning to establish these requirements. In order to ensure that the bridges behave correctly regardless of the topology of the surrounding bridges and LANs, the Rebeca, modular verification techniques are applied. These techniques are shown to be efficiently applicable in model checking... 

Smart systems in general, and specifically neural networks, are expected to be of great assistance in large scale matrix computation. However it was necessary to work with smaller problems at first step. To this end, a method based on using perceptrons and Kohonen networks for determining the first three modal frequencies of frames of up to 20 stories high and two bays wide from their stiffness and mass matrices, was developed. This paper introduces this modular network as a preferable alternative for designing smart systems for learning large scale mapping problems in structural engineering, and in addition, reports the successful application of this modular network to the eigenvalue and... 

During design, microsatellites are subject to different changes like the changes in weight, location and dimension of parts and elements of subsystems and the payload. These changes should be accumulated by the structure subsystem in a way that some key structural parameters like the center of gravity (CG) and inertia moments remain unchanged. This subject is also important regarding the design of a modular structure of a satellite. In the present study it is tried to accommodate any changes in weight and location of any part(s) and element(s) of a microsatellite by optimum (minimum) rearrangement of other parts on their plane of rest in order to keep the CG and inertia moments unchanged....