Sharif Digital Repository

We introduce a simple representation for irreducible spherical tensor operators of the rotation group of arbitrary integer or half integer rank and use these tensor operators to construct matrix product states corresponding to all the variety of valence bond states proposed in the Affleck-Kennedy-Lieb- Tasaki (AKLT) construction. These include the fully dimerized states of arbitrary spins, with uniform or alternating patterns of spins, which are ground states of Hamiltonians with nearest and next-nearest-neighbor interactions, and the partially dimerized or AKLT/valence bond solid states, which are constructed from them by projection. The latter states are translation-invariant ground states... 

In this paper, a new graph product, called Edge Graph Product (EGP) is proposed by replacing each edge in the multiplicand graph by a copy of the multiplier graph via two candidate nodes. The edge product, unlike other products already proposed, results in a graph whose number of edges is numerical product of the number of the edges in the multiplicand and multiplier graphs, and the number of vertices is not equal to the numerical product of the number of vertices in the multiplicand and multiplier graphs. After formal definition of the new product, some basic properties of the product operator are studied. We then address Hamiltonian, Eulerian and routing properties of the new product, and... 

Let Mm (D) be a finite dimensional F-central simple algebra. It is shown that Mm (D) is a crossed product over a maximal subfield if and only if GLm (D) has an irreducible subgroup G containing a normal abelian subgroup A such that CG (A) = A and F [A] contains no zero divisor. Various other crossed product conditions on subgroups of D* are also investigated. In particular, it is shown that if D* contains either an irreducible finite subgroup or an irreducible soluble-by-finite subgroup that contains no element of order dividing deg (D)2, then D is a crossed product over a maximal subfield. © 2007 Elsevier Inc. All rights reserved  

We investigate quantum phase transitions in ladders of spin- 1 2 particles by engineering suitable matrix product states for these ladders. We take into account both discrete and continuous symmetries and provide general classes of such models. We also study the behavior of entanglement between different neighboring sites near the transition point and show that quantum phase transitions in these systems are accompanied by divergences in derivatives of entanglement. © 2007 The American Physical Society  

An analytic expression for energy and angular dependence of a secondary charged lepton in the decay of a polarized top quark with anomalous tWb couplings in the presence of all anomalous couplings are derived. The angular distribution of the b-quark is derived as well. It is presented that the charged lepton spin correlation coefficient is not very sensitive to the anomalous couplings. However, the b-quark spin correlation coefficient is sensitive to anomalous couplings and could be used as a powerful tool in the search for non-SM coupling. © 2007 IOP Publishing Ltd  

Distilleries wastewater is an important environmental problem due to its high BOD and COD content, and toxic materials such as phenolic compounds, and low pH. Direct and continuous discharge of this effluent to the soil reduces the quality of soil and destroys agricultural crops. In addition, its discharge to rivers and sea will seriously affect aquatic life. In order to prevent environmental hazards, a number of biological, chemical and physical methods have been introduced for treatment of this wastewater. Chemical and physical methods are based on surface sorption, ion exchange, membrane processes and chemical oxidations. In biological methods, anaerobic processes are more economical than... 

In this study an analytical model has been developed to describe air pressure and residual air mass variations in pressure die casting for atmospheric venting. During injection of molten metal into a die cavity, air is evacuated from the cavity through vents. In this study, the influences of air velocity and friction factor due to temperature dependent viscosity and vent roughness change have been investigated. The results of the model show that there is a critical area ratio over which a quasi steady state is reached, therefore, the air pressure in the cavity remains constant. In addition, for each area ratio there is a critical/ minimum time ratio below which outlet Mach number is not... 

The upgradation of the Kerman cement plant in Iran was discussed. It produces type 2,5 and pozzolanic cements which constitute almost 4.2% of the cement used in Iran. A short description of the process used, and some observations and recommendations about the plant were also provided  

PID controllers have been used for many years in industry and if a controller is well tuned, its performance is acceptable for many industrial processes. When the operating point is changed, due to nonlinear behavior of most processes, the controller should be retuned. In this regard, several self-tuning PID controllers are proposed in the literature. In this paper, four such algorithms are compared through simulation and experimental studies. In the simulation study, the effects of factors such as process pole locations, non-minimum phase behavior and model changes on the performance of the schemes are investigated. Simulation and experimental results demonstrate that one of the schemes... 

A proper vertex coloring of a graph G is called a star coloring if every two color classes induce a forest whose each component is a star, which means there is no bicolored P4 in G. In this paper, we show that the Cartesian product of any two cycles, except C3C3 and C3C5, has a 5-star coloring. © 2022 World Scientific Publishing Company  

Nowadays, companies strive to survive in a competitive global environment. Reduction of product development cycle plays a major role in market penetration and cost reduction. To speed up product development/modifications, it is suggested to adopt a collaborative product development approach. Collaborative design and manufacture requires an integrated platform to support related CAx product data models. To integrate CAx product data, a number of solutions are proposed. The most successful solution is adopting the STandard for Exchange of Product Data (STEP). In the course of the STEP standard structure and procedure development, two approaches can be recognised: classical and modular. The... 

The objective of this paper is to provide a framework to integrate the existence of products with imperfect-quality items, inspection errors, rework and scrap items into a single Economic Production Quantity (EPQ) model. To achieve this objective, a suitable mathematical model is defined and the optimal production lot size that minimises the total cost is obtained. Sensitivity analysis is carried out for this model. The sensitivity analysis results indicate that the model is very sensitive to defective proportions and type 1 errors of inspection. Nowadays, given the progress made, inspection errors are often ignored. But the findings of this study show that the values of EPQ and total cost... 

In this paper, we define the concept of integral for an arbitrary group, and we try to answer this question: Which groups can be considered as a commutator subgroup? For instance, we will show that symmetric group Sn for n ≥ 3, generalized quaternion group Q2n for n ≥ 4 and Dihedral group Dn for n ≥ 3 cannot occur as commutator subgroup of any group. Moreover, we characterize all finite groups with the cyclic commutator subgroup isomorphic to Z2n or Z3n.© 2017, Copyright © Taylor & Francis Group, LLC  

The Cartesian and Composition products are two well known graph products, also applied to interconnection networks area. The Cartesian and Composition network products possess great characteristics of fault resilience according to their high connectivity. In this paper, we study the existence and construction of parallel routing paths in these two well-known product networks. To prove the existence of certain number of parallel paths in these product networks, we need to compute their connectivity. By assuming the availability of certain number of faulty nodes, we propose some new shortest-path parallel routing algorithms. These algorithms can be used both in faulty networks and to route... 

To monitor the quality of a multi-attribute process, some issues arise. One of them being the occurrence of a high number of false alarms (type I error) and the other an increase in the probability of not detecting defects when the process is monitored by a set of independent uni-attribute control charts. In this paper, based upon the artificial neural network capabilities we develop a new methodology to overcome this problem. We design a perceptron neural network to monitor either the proportions of several types of product nonconformities (instead of using several np charts) or the number of different types of defects (instead of using several c charts) in a product. Moreover, while the... 

"Product" and "process" are two mutually orthogonal and important aspects of software. As Part 1 discusses "product", Part 2 discusses "process". "Process" is independent of "product" and is used commonly by various "producers". This paper first explains the structure of "process" and then introduces important technique by "divide and conquer". Various important management issues are discussed  

In this paper, we present an axiomatic modeling of lean production system design, using process variables (PVs). So far, we had developed a model for conceptual design of lean production systems by means of FR-DP relationships, the key characteristics of axiomatic design (AD) methodology, appeared in the proceedings of Second International Conference of Axiomatic Design. Albeit the model in question was thorough enough to be applied in various cases, its embedded abstract principles hamper straightforward applications and the required resources, tools, and techniques are not clarified. In AD terms, it lacks PVs created by mapping the design parameters (DPs) to the process domain to clarify... 

This paper considers an imperfect production system in which defective items are produced in. each cycle of production. We assume that the defectives produced within each cycle will be reworked immediately after each production run is completed. We also assume some scrap is produced and detected during the rework period. Further, we assume that the number of scrapped items produced during the rework period is a random variable. For this system, using some theorem from the renewal theory, the expected total cost function per unit time is derived and the optimal batch quantity is obtained  

Today's information technology capabilities enable the enterprises to increase the manufacturing collaboration and interoperability among their different departments. These departments are engaged in different product development processes from design to manufacturing. INFELT STEP is a three-layered platform. These layers have functions and structures that enable the INFELT STEP platform to manage the product development collaboration among different CAD/CAM application software with an integrated product data structure. INFELT STEP has structures and functions in its interoperability layer that enable different CAD/CAM application software and CNC post processors to use their own data...