Sharif Digital Repository

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... 

In this work we study the spherical symmetric solutions of f(R) gravity in the metric formalism. We show that for a generic f(R) gravity, the spherical symmetric solution is consistent with the modified gravity equations except in the case of imposing an extra condition for the metric. © 2009 World Scientific Publishing Company  

We use metric formalism in f(R) modified gravity to study the dynamics of various systems from the solar system to the cosmological scale. We assume an ansatz for the derivative of action as a function of distance and describe the Pioneer anomaly and the flat rotation curve of the spiral galaxies. Having the asymptotic behavior of action, we propose the action of f(R)=(R+Λ)(1+ln (R/Rc)/(R/R0+2/α)) where in galactic and solar system scales it can recover our desired form. The vacuum solution of this action also results in a positive late time acceleration for the Universe. We fix the parameters of this model, comparing with the Pioneer anomaly, rotation curve of spiral galaxies, and supernova... 

Regarding the geometric structural characteristics of innovative dual cooled annular fuel and the possibility of heat split and flow distribution among the internal and external channels, the development of new computational tools is essential for estimating safety margins and accurate assessment of its thermal-hydraulic performance. The SADAF code (Subchannel Analysis Dual cooled Annular Fuel) by COBRA-EN code is developed for this purpose. In the SADAF code, using COBRA-EN code for subchannel analysis in internal and external subchannels, a program has been developed to compute new variables that need to be considered in the thermal-hydraulic assessment. Also, fuel heat transfer... 

We consider M/M/1/∞ systems with inventory in which completing each service in the queueing system requires an on-hand inventory. Continuous review (r, Q) policy is considered for the inventory system, and lead times are assumed to be mixed exponentially distributed. During stockout, arriving demands get rejected from the queue and become lost (lost sale situation). We derive stationary distribution of product form of joint queue length and on-hand inventory. The resulting distribution is employed to compute performance measures which can be used to derive the optimal policy. Optimal order size for predetermined reorder policy is initially determined and finally, optimal reorder point and... 

We consider an M/M/1 queueing system with inventory under the (r,Q) policy and with lost sales, in which demands occur according to a Poisson process and service times are exponentially distributed. All arriving customers during stockout are lost. We derive the stationary distributions of the joint queue length (number of customers in the system) and on-hand inventory when lead times are random variables and can take various distributions. The derived stationary distributions are used to formulate long-run average performance measures and cost functions in some numerical examples  

In this paper, a new 1/4 rate clock linear phase detector (PD) structure for PLL-based clock and data recovery (CDR) circuits will be suggested. The proposed topology offers a more suitable PD for high speed applications compared to the conventional topologies. The effect of duty cycle variation on the operation of CDR has been also studied. Designed in a 0.18μm CMOS technology, the proposed PD consumes 16mA from a 1.8V voltage supply. © 2006 IEEE  

In this research, a numerical investigation is done on the effect of employing the new combined vortex generators, the twisted tape turbulator and Al2O3-H2O nanofluid as the involved base fluid. Such study is carried out on the behavior of the heat transfer rate and the pressure drop of a double pipe heat exchanger. Accordingly, the response surface methodology (RSM) grounded on the central composite design (CCD) is used for acquiring the optimized geometry of the combined vortex generator and twisted tape turbulator. In order to have the maximum Nusselt number and minimum friction factor, twenty cases with different pitches ratio Pil=0.09-0.18, angles (θ=0-30°) and Reynolds numbers (Re =... 

Optimized conditions of hot and cold rolling followed by annealing can result in a balance between recrystallization and rolling textures in order to reduce the planar anisotropy of brass sheets. In this work, the effect of finish rolling temperature, cold reduction and annealing temperature on texture development has been investigated. It is shown that uniform deformation at higher finishing temperature is responsible of formation of a severe Cube and G texture components. In contrast, mechanical twinnings are widely formed at low finishing temperatures. There is also a direct relation between the intensity of Cube component and the amount of cold reduction  

In this paper, a new method is proposed for motion vector steganalysis using the entropy value and its combination with the features of the optimized motion vector. In this method, the entropy of blocks is calculated to determine their texture and the precision of their motion vectors. Then, by using a fuzzy cluster, the blocks are clustered into the blocks with high and low texture, while the membership function of each block to a high texture class indicates the texture of that block. These membership functions are used to weight the effective features that are extracted by reconstructing the motion estimation equations. Characteristics of the results indicate that the use of entropy and... 

Abstract: Robotics and Artificial Intelligence (AI) have always been among the most popular topics in science fiction (sci-fi) movies. This paper endeavors to review popular movies containing Fictional Robots (FR) to extract the most common characteristics and interesting design ideas of robots portrayed in science fiction. To this end, 134 sci-fi films, including 108 unique FRs, were investigated regarding the robots’ different design aspects (e.g., appearance design, interactive design and artificial intelligence, and ethical and social design). Also, in each section of this paper, some characteristics of FRs are compared with real social robots. Since some researches point to the...