Sharif Digital Repository

Intermittent connectivity is an intrinsic feature of vehicular ad hoc networks (VANETs) in sparse situations. This type of network is in fact an example of delay and disruption tolerant networks (DTNs). In this paper, we focus on a typical two-way street and analytically evaluate the maximum stable throughput and the average delay for packet forwarding along the street. To this end, we map the mobility patterns of the vehicles with different speeds onto suitable parameters of a BCMP queueing network and derive the location density of vehicles. Then, we employ another queueing network in order to model opportunistic multi-hop packet forwarding along the street with respect to the... 

The compounds with composition GdBa2Cu3-xV xO7-δ and x = 0.0, 0.05, 0.1, 0.15, 0.2 and 0.3 have been prepared by the solid-state reaction method. The XRD spectra indicate single-phase formation of the compounds. The transition temperature decreases considerably with vanadium concentration to Tc = 26.4 K for x = 0.3. The host sample is in the orthorhombic phase, but by increasing the V content the structure approaches the tetragonal phase, and for x = 0.3 the structure is nearly tetragonal. The normal state resistivity has been compared with 2D-VRH, 3D-VRH, and CG regimes, which shows that the 2D-VRH and CG are in better agreement for our samples. The localization length is calculated for the... 

The mobility pattern of users is one of the distinct features of vehicular ad hoc networks (VANETs) compared with other types of mobile ad hoc networks (MANETs). This is due to the higher speed and the roadmap-restricted movement of vehicles. In this paper, we propose a new analytical mobility model for VANETs based on product-form queueing networks. In this model, we map the topology of the streets and the behavior of vehicles at both intersections and different parts of the streets onto different parameters of a BCMP1 open queueing network comprising M/G/nodes. This model represents a sparse situation for VANETs. To include the effect of dense situation on the mobility model, we modify the... 

Many chemical production systems encounter with a functionally flexible workplace which need multi-skilled workers. This research integrates the multi-skilled project scheduling problem with the resource investment problem which aims to obtain concurrent optimal policy of project scheduling and skills’ recruitment. The objective of the proposed model is minimization of total recruitment cost for different levels of the skills. An integer programming formulation is developed for the problem, and it is validated through solving several small scale instances using the GAMS software. To tackle real-life problem scales, a genetic-based and a particle-swarm-based algorithm with calibrated... 

One of the major problems in underdetermined Sparse Component Analysis (SCA) is the appropriate estimation of the mixing matrix, A, in the linear model x(t) = As(t), especially where more than one source is active at each instant of time (It is called 'multiple dominant problem'). Most of the previous algorithms were restricted to single dominant problem in which it is assumed that at each instant, there is at most one single dominant component. Moreover, because of high computational load, all present methods for multiple dominant problem are practical only for small scale cases (By 'small scale' we mean that the average number of active sources at each instant, k, is less than 5). In this... 

Satisfying the clients' uncompromising priorities is a challenge for decision makers of organizations that face multiple projects. This paper considers an organization with a multi-skilled workforce working on several predetermined projects under time-of-use energy tariffs where distributed load energy usage is the primary concern of energy suppliers. This paper also considers different time-of-use energy tariffs, which are among the most common strategies to reach a more balanced energy utilization. The problem is stated as a bi-objective mixed-integer programming model containing two conflicting objectives; to minimize the total cost of the multi-skilled workforce and obtain a sustainable... 

Satisfying the clients' uncompromising priorities is a challenge for decision makers of organizations that face multiple projects. This paper considers an organization with a multi-skilled workforce working on several predetermined projects under time-of-use energy tariffs where distributed load energy usage is the primary concern of energy suppliers. This paper also considers different time-of-use energy tariffs, which are among the most common strategies to reach a more balanced energy utilization. The problem is stated as a bi-objective mixed-integer programming model containing two conflicting objectives; to minimize the total cost of the multi-skilled workforce and obtain a sustainable... 

For an undirected graph G, a zero-sum flow is an assignment of non-zero real numbers to the edges, such that the sum of the values of all edges incident with each vertex is zero. It has been conjectured that if a graph G has a zero-sum flow, then it has a zero-sum 6-flow. We prove this conjecture and Bouchet's Conjecture for bidirected graphs are equivalent. Among other results it is shown that if G is an r-regular graph (r ≥ 3), then G has a zero-sum 7-flow. Furthermore, if r is divisible by 3, then G has a zero-sum 5-flow. We also show a graph of order n with a zero-sum flow has a zero-sum (n + 3)2-flow. Finally, the existence of k-flows for small graphs is investigated  

A nonlinear integer programming model is developed in this article to solve redundancy allocation problems with multiple components having different failure rates in the series–parallel configuration using an active strategy. The main objective of this research is to select the number and the type of each component in subsystems so as the reliability of the system under certain constraints is maximized. To this aim, a weighted K-means clustering method is proposed, in which the analytical network process is employed to assign weights to the components of each cluster. As the proposed model belongs to the class of nondeterministic polynomial-time hardness problems, precise solution methods... 

Objective: This systematic review and meta-analysis was performed to determine the prevalence rate of influenza virus from different parts of Middle East region, and present an overall relative frequency (RF) for this region. Methods: The authors performed a systematic literature review from several reliable databases such as PubMed, ISI Web of Science and Scopus during 2000–2016. Furthermore, the keywords of this research were ‘Influenza’, ‘Subtype’, ‘Seroprevalence’, ‘Incidence’, ‘Seroepidemiology’, ‘H1N1’, ‘H3N2’, ‘H5N1’, ‘H9N2’, ‘Middle-East’ and ‘Meta-analysis’. The reported data were selected according to inclusion and exclusion criteria. Results: The authors selected 71 studies out of... 

Aim: The aim of this study was to assess the relationship between microRNAs and viral and immunological markers in HIV-1 infection. Materials & methods: The expression level of miRNAs was evaluated in 60 HIV-1 patients and 20 healthy controls using real-time PCR assays. Results: The results showed that among all miRNAs, miR-29 and miR-150 were significantly downregulated in HIV-1 patients compared with healthy controls, while miR-155 and miR-223 were significantly upregulated compared with healthy controls (p < 0.001 for all comparisons). Conclusion: The mentioned miRNAs seem to influence the clinical progression of HIV-1 infection in naive patients. Moreover, determining the profiles of...