Sharif Digital Repository

This study considers a two-echelon inventory system with one central warehouse and a number of non-identical retailers with Poisson demands, constant lead times, and lost sales for a single item. The warehouse works as a cross-docking terminal with no inventory and coordinates shipments to retailers. We apply the Joint order (1, T) policy in such an inventory system. In the standard (1, T) policy, the warehouse sends one unit of the item to each retailer in a fixed cycle time, which is calculated by considering each retailer separately. In the joint order (1, T) policy, the warehouse decides to replenish one unit of the item for each retailer in a cycle time which is adjusted to be an... 

The mixed-convection flow from a hot vertical impinging jet on a colder horizontal disc has been studied. The geometry is analogous to a conventional burning gas cooktop. A numerical simulation of the system has been carried out using the finite-element method to study the dependence of fluid flow and heat transfer on the geometric, thermal, and fluid flow parameters. Results show that heat transfer efficiency versus several parameters such as inlet velocity magnitude and flue gas temperature has an optimum value, in which heat transfer efficiency is maximum. With thermal conductivity of the solid wall, velocity angle, and solid wall diameter heat transfer efficiency has increasing behavior.... 

Common characteristics of inventory systems include uncertain demand and restrictions such as budgetary or storage space constraints. Several authors have examined budget constrained multi-item stochastic inventory systems controlled by continuous review policies without considering marginal shortage costs. Existing models assume that purchasing costs are paid at the time an order is placed, which is not always the case since in some systems purchasing costs are paid when orders arrive. In the latter case the maximum investment in inventory is random since the inventory level when an order arrives is a random variable. Hence payment of purchasing costs on delivery yields a stochastic budget... 

We present a general study on a high performance supercapacitor based on intercalated reduced graphene oxide with carbon black nanoparticles. Graphene oxide sheets were synthesized by oxidation and exfoliation of natural graphite and were reduced using hydroiodic acid in the presence of carbon black nanoparticles. Graphene paper was fabricated by one-step procedure via simultaneous reducing and drying the aqueous solution of mixed carbon black nanoparticles and graphene oxide on a conductive substrate. Transmission electron microscopy confirmed the intercalation of carbon black nanoparticles into reduced graphene oxide sheets, preventing them from restacking during the fabrication of paper.... 

A mathematical framework to model the heat transfer efficiency of cooking pots is proposed and exploited in this paper. The model consists of combining the experimental results and the statistical data of Residential Energy Consumption Survey (RECS) of Iran with a soft-computing concept such as neural network. Using neural network results, the variations of the efficiency with various parameters have been studied. It is shown that Group Method of Data Handling (GMDH)-type neural network can effectively model and predict thermal efficiency, as a function of important input parameters for a conventional cooking pot. Results show that efficiency increases with increasing diameter to flame... 

Secure routing is a major key to service maintenance in ad hoc networks. Ad hoc nature exposes the network to several types of node misbehavior or attacks. As a result of the resource limitations in such networks nodes may have a tendency to behave selfishly. Selfish behavior can have drastic impacts on network performance. We have proposed a Misbehavior-Tolerant Multipath Routing protocol (MTMR) which detects and punishes all types of misbehavior such as selfish behavior, wormhole, sinkhole and grey-hole attacks. The protocol utilizes a proactive approach to enforce cooperation. In addition, it uses a novel data redirection method to mitigate the impact of node misbehavior on network...