Sharif Digital Repository

We have studied the phase diagram of the one-dimensional S= 1 2 XXZ model with ferromagnetic nearest-neighbor and antiferromagnetic next-nearest-neighbor interactions. We have applied the quantum renormalization group (QRG) approach to obtain stable fixed points and the scaling of coupling constants. The QRG prescription has to be implemented to the second order of interblock interactions to obtain a self-similar Hamiltonian after each step of the QRG. This model shows a rich phase diagram which includes quantum spin-fluid and dimer phases in addition to the classical Néel and ferromagnetic ones. We have found the border between different phases by tracing the scaling of coupling constants.... 

In this paper, seller-buyer supply chain coordination with general side-payment contracts is introduced to gain the maximum possible chain profit. In our model, the logistics costs for both buyer and seller are considered and the final demand is also supposed to be a decreasing function of the retail price. Since parties aim to maximize their individual profits, the contractual parameters are set in a way that these decisions become aligned with system optimal decisions. Therefore, a side payment contract is suggested in our model to assign the chain surplus profit to the chain members such that they have no intention to leave the coalition. Then, we change the contract into a quantity... 

In this paper1 we consider higher isoperimetric numbers of a (finite directed) graph. In this regard we focus on the nth mean isoperimetric constant of a directed graph as the minimum of the mean outgoing normalized flows from a given set of n disjoint subsets of the vertex set of the graph. We show that the second mean isoperimetric constant in this general setting, coincides with (the mean version of) the classical Cheeger constant of the graph, while for the rest of the spectrum we show that there is a fundamental difference between the nth isoperimetric constant and the number obtained by taking the minimum over all n-partitions. In this direction, we show that our definition is the... 

Omega polynomial was introduced by Diudea. Following Omega polynomial, the Sadhana polynomial was defined by Ashrafi et al. In this paper we compute Omega and Sadhana polynomials of three classes of dendrimers  

The Zagreb indices have been introduced more than thirty years ago by Gutman and Trinajstić. In this paper we introduce a new version of Zagreb indices and then we compute them for an infinite family of nanostar dendrimers  

In this paper. 11This article is a revised version of Daneshgar and Hajiabolhassan (2008) [19] distributed on arXiv.org (1'st, Jan. 2008). we consider higher isoperimetric numbers of a (finite directed) graph. In this regard we focus on the nth mean isoperimetric constant of a directed graph as the minimum of the mean outgoing normalized flows from a given set of n disjoint subsets of the vertex set of the graph. We show that the second mean isoperimetric constant in this general setting, coincides with (the mean version of) the classical Cheeger constant of the graph, while for the rest of the spectrum we show that there is a fundamental difference between the nth isoperimetric constant and... 

Let G be a graph. The first and second Zagreb index of G is defined as M1(G)= Σ degG(V)2 and M2(G)= Σ degG(u)degG(V) respectively. In this paper we compute Zagreb indices of chain graphs  

The purpose of this paper is to adopt and analyze a new ordering policycalled one-for-one-period policy in a multi-echelon supply chain consisting ofone retailer and a series of TV suppliers. The main advantage of adopting theone-for-one-period (7,7) ordering policy for retailers is the elimination ofuncertainty for supplier which leads to total elimination of the safety stocksat all suppliers. This in turn leads to the reduction of the total system costsand in case any supplier's ordering cost is negligible it can even eliminate theneed for him to carry any inventory. In addition to this advantage, thenumerical results show that the application of this new policy for the retailerleads to... 

Biodiesel is an attractive renewable energy in Iran. However, the concerns for food security, emissions, and water requirement move us towards developing the analytical framework to study emission-water nexus of biodiesel via the multi objective sustainable planning of biodiesel supply chain. Here, the literature of biodiesel in Iran is comprehensively reviewed and main issues are discussed. Then, a supply chain planning model is applied to depict the optimal path ways to minimize costs, net emission, and water use in Iran during 25 years. The microalgae via open ponds and jatropha cultivation reduce the total costs and improve negative emissions. The jatropha optimizes the water use and... 

Purpose: In this paper, the joint replenishment problem is modeled for a two-level supply chain consisting of a single supplier and multiple retailers that use the vendor-managed inventory (VMI) policy for several products. This paper aims to find the optimal number of products to order in both policies, the optimal times at which each retailer orders the products in the traditional policy and the optimal times at which the supplier orders the product in the VMI policy. Design/methodology/approach: The problem is first formulated into the framework of a constrained integer nonlinear programming model; then, the problem is solved using a teacher-learner based optimization algorithm. As there... 

Cell lysis is the most important first step for molecular biology and diagnostic testing. Recently, microfluidic systems have attracted considerable attention due to advantages associated with automation, integration and miniaturization, especially in resource-limited settings. In this work, novel centrifugal microfluidic platforms with new configurations for chemical cell lysis are presented. The developed systems employ passive form of pneumatic and inertial forces for effective mixing of lysis reagents and cell samples as well as precise fluidic control. Characterizations of the developed Lab-on-a-Discs (LoaDs) have been conducted with dyed deionized (DI) waters and white blood cells... 

We have studied the phase diagram and entanglement of the one-dimensional Ising model with Dzyaloshinskii-Moriya (DM) interaction. We have applied the quantum renormalization-group (QRG) approach to get the stable fixed points, critical point, and the scaling of coupling constants. This model has two phases: antiferromagnetic and saturated chiral ones. We have shown that the staggered magnetization is the order parameter of the system and DM interaction produces the chiral order in both phases. We have also implemented the exact diagonalization (Lanczos) method to calculate the static structure factors. The divergence of structure factor at the ordering momentum as the size of systems goes... 

Given integers t, k, and v such that 0 ≤ t ≤ k ≤ v, let Wt k (v) be the inclusion matrix of t-subsets vs. k-subsets of a v-set. We modify slightly the concept of standard tableau to study the notion of rank of a finite set of positive integers which was introduced by Frankl. Utilizing this, a decomposition of the poset 2[v] into symmetric skipless chains is given. Based on this decomposition, we construct an inclusion matrix, denoted by Wover(t, -) k (v), which is row-equivalent to Wt k (v). Its Smith normal form is determined. As applications, Wilson's diagonal form of Wt k (v) is obtained as well as a new proof of the well-known theorem on the necessary and sufficient conditions for... 

Functional relationship between supplier and buyer in an open market place leads to investigate the role of both quantifiable and non-quantifiable parameters in coordination mechanism with the aim of achieving higher performance in supply chain activities. Here, we develop a supply chain model and a new agent to analyze and simulate the players' behavior in the network. A cooperative game theory framework is utilized between buyer and supplier in order to increase the supply chain performance. The study is supported by presenting SC Net Optimizer as a tool for implementing the proposed coordination mechanism and evaluates the performance of the chain by simulation using stochastic Petri nets... 

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... 

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  

This paper studies inventory and pricing policies in a non-cooperative supply chain with one supplier and several retailers who are involved in producing, delivering and selling a single product. We consider inventory policies in an information-asymmetric vendor managed inventory. The study consists of different scenarios where a supplier produces the product at the wholesale price to multiple retailers. The retailers also distribute the product in dispersed and independent markets at retail selling prices. The demand rate for each market is a non- decreasing concave function of the marketing expenditures of both local retailers and the manufacturer, but a non-increasing and convex function... 

The increasing level of customer awareness and application of environmental laws by governments, on the one hand, and the increasing number of competitors, on the other hand, has obliged industry owners to include green activities in the design of the supply chain network. Green activities include any type of action that reduces environmental degradation. Hence, this study seeks to develop a bi-objective, mixed integer linear programming (MILP) model for designing a green supply chain network. In the proposed model, the minimisation of costs and detrimental environmental effects are discussed. LP metric method is used to solve the bi-objective model and the proposed model is run by using... 

Now days supply chain systems operate in an operational environment with high uncertainty. Customer globalization, increase of natural and manmade disasters, outsourcing in far distances have increased uncertainty. Flexibility as a capability can help systems included supply chains respond to uncertainty and deliver value to their users. auto supply chain is the one that has suffered from these disasters. This paper encapsulates operational environment uncertainty through scenario development, then scores the scenarios based on some proxies. Design structure matrix is proposed to show the typical auto supply chain relationships before scenario occurring consequences and after that. in the... 

In this paper a two-echelon supply chain consisting of a supplier and aretailer is considered, Customers refer to retailer according to a Poissonprocess and retailer uses one for one inventory policy. Supplier followscontinuous review (r,Q) policy. Satisfying each demand which arrives to thesupplier needs an on hand-inventory and a process/service. Process/service andreplenishment lead times are random variables which are exponentiallydistributed. During a period that supplier has non zero on-hand inventory,arriving demands from retailer join the queue. But when supplier has no on-handinventory retailer buys product from the other source with zero lead time andadditional cost. In this paper...