Sharif Digital Repository

A solution to the imbalance of vehicles in one-way carsharing systems is vehicle relocation which involves staff members to redistribute the vehicles between stations. Vehicle relocation, however, can lead to an imbalance of staff members between stations. Thus, staff members, themselves, need to be relocated between stations to perform the vehicle relocations. This study addresses the joint optimization of vehicle relocation and staff rebalancing using two integrated multi-traveling salesman formulations. Results show that fleet size is more sensitive to demand than staff size, staff size is inversely related to vehicle cost, and that vehicle relocation time increases with vehicle cost  

The effects of temperature, seed mass and agitation rate on agglomeration kinetics of aluminum hydroxide in Bayer process have been studied in a batch system. Collected raw data were analyzed and the kinetics data of agglomeration were derived through simulation of the process using a pre-developed software. The results showed that agglomeration kinetics constant (agglomeration kernel) increases with increase in temperature and agitation rate. Moreover a maximum value of agglomeration rate versus added seed mass was observed. Furthermore the magnitude of calculated activation energy of agglomeration was close to that of growth  

In some quality control applications, processes consist of multiple components, stations or stages to finish the final products or the services. Some quality characteristics in each stage of these processes (called multistage processes) can be represented by a relationship between a response and one or more explanatory variables which is named as profile. In this paper, a general model is proposed for monitoring multivariate profiles in multistage processes. To this aim, the multivariate form of the U transformation approach is first used to remove the effect of the cascade property between the stages. Then, three control schemes are employed to monitor the parameters of multivariate simple... 

In this investigation a theoretical model based on artificial neural network (ANN) has been developed to predict porosity percent and correlate the chemical composition and cooling rate to the amount of porosity in Al-Si casting alloys. In addition, the sensivity analysis was performed to investigate the importance of the effects of different alloying elements, composition, grain refiner, modifier and cooling rate on porosity formation behavior of Al-Si casting alloys. By comparing the predicted values with the experimental data, it is demonstrated that the well-trained feed forward back propagation ANN model with eight nodes in hidden layer is a powerful tool for prediction of porosity... 

In this investigation, a neural network model was used to predict mechanical properties of dual phase (DP) steels and sensivity analysis was performed to investigate the importance of the effects of pre-strain, deformation temperature, volume fraction and morphology of martensite on room temperature mechanical behavior of these steels. In order to train the neural network, dual-phase (DP) steels with different morphology and volume fractions of martensite were deformed between 2 and 8%, at high temperature range of 150-450 °C. The results of this investigation show that there is a good agreement between experimental and predicted values and the well-trained neural network has a great... 

The presence of energy hubs in the future vision of energy networks creates an opportunity for electrical engineers to move toward more efficient energy systems. At the same time, it is envisioned that smart grid can cover the natural gas network in the near future. This paper modifies the classic Energy Hub model to present an upgraded model in the smart environment entitling "Smart Energy Hub". Supporting real time, two-way communication between utility companies and smart energy hubs, and allowing intelligent infrastructures at both ends to manage power consumption necessitates large-scale real-time computing capabilities to handle the communication and the storage of huge transferable... 

An efficient and one-pot process has been developed for the synthesis of novel benzo[4,5]imidazo[2,1-b]pyrimido[4,5-d][1,3]thiazine-2,4(3H)-diones and benzo[4,5]imidazo[2,1-b][1,3]thiazin-4-ones from CH acids, aldehydes and 2-mercaptobenzimidazole using hexyltriphenylphosphonium bromide ionic liquid (HTPB) as a green promoter and solvent at ambient temperature. The reaction afforded products in high yields and short reaction times, bypassing the conventional harsh reaction conditions and without the need for using volatile solvents. In addition, we evaluated the anti-cancer activity of these compounds on different cancer cells, including A431, PC3, and Panc1 and HDF (human dermal fibroblast)... 

In this paper, we consider the problem of secret key agreement in state-dependent 3-receiver broadcast channels. In the proposed model, there are two legitimate receivers, an eavesdropper and a transmitter where the channel state information is non-causally available at the transmitter. We consider two setups. In the first setup, the transmitter tries to agree on a common key with the legitimate receivers while keeping it concealed from the eavesdropper. Simultaneously, the transmitter agrees on a private key with each of the legitimate receivers that needs to be kept secret from the other legitimate receiver and the eavesdropper. For this setup, we derive inner and outer bounds on the... 

The presence of energy hubs and the advancement in smart grid technologies have motivated system planners to deploy intelligent multicarrier energy systems entitled "smart energy hub" (S.E. Hub). In this paper, we model S.E. Hub, and propose a modern energy management technique in electricity and natural gas networks based on integrated demand side management (IDSM). In conventional studies, energy consumption is optimized from the perspective of each individual user without considering the interactions with each other. Here, the interaction among S.E. Hubs in IDSM program is formulated as a noncooperative game. The existence and uniqueness of a pure strategy Nash equilibrium (NE) is proved.... 

In recent years, there have been significant developments of applications related to 'Energy Hub' and 'Smart Grid' concepts. Synergy effect of the coupling between electricity and natural gas infrastructures, and approaching energy systems to the smart grid environment leads us to introduce a new solution. This solution is entitled 'Smart Energy Hub' (S. E. Hub). Simply stated, the S. E. Hub models a multicarrier energy system in a smart grid environment. The evolution of the smart grid heavily relies on the utilization and the integration of modern information technologies. Therefore, we suggest that the information technology industry should be involved to facilitate the information... 

This study investigated the effects of combined utilization of wollastonite particles and recycled waste ceramic aggregate (RWCA) on high strength concrete (HSC) properties. Two groups of mixtures were manufactured: 1) concrete mixtures in which cement was partially replaced with wollastonite at values ranging from 10% to 50%, and 2) mixtures in which wollastonite was used at the aforementioned dosages and 50% of natural coarse aggregate was replaced with RWCA. In addition, 10% of cement weight micro-silica was added to all mixtures. The concrete behavior in terms of strength, durability, resistance against acidic environment, and performance under elevated temperatures ranging from 20 °C to... 

Purpose: This study aims to systematically review the economic complexity literature to advance the knowledge on its contribution to building regional competitiveness. Design/methodology/approach: In this study, we did a systematic review of 111 relevant papers. In this regard, we did a thematic analysis on all the collected papers, which led to a two-level processed approach. In the first level, the contributions of the reviewed articles have been classified into three main streams. In the second level, the findings under each contribution category are analyzed and explained. This approach led to a thematic network demonstrating economic complexity and the dynamics of regional... 

In this paper, an artificial neural network (ANN) model has been developed to predict the yield and tensile strengths of hot pressed NiAl intermetallic compound based on the experimental data from Albiter et al. [A. Albiter, M. Salazar, E. Bedolla, R.A.L. Drew, R. Perez, Mater. Sci. Eng. A 347 (2003) 154]. The predicted results, with a correlation relation between 0.9791 and 0.9921, show a very good agreement with the experimental values. Furthermore, the sensitivity analysis was performed to investigate the importance of the effects of chemical composition and temperature on the mechanical behavior of hot pressed NiAl intermetallic compound. © 2008 Elsevier B.V. All rights reserved  

This paper proposes a fuzzy-based speed controller for the doubly fed induction generator (DFIG)-based wind turbines with the rotor speed and wind speed inputs. The controller parameters are optimized using the particle swarm optimization algorithm. To accelerate tracking the maximum power point trajectory, the conventional controller is augmented with a feed-forward compensator, which uses the wind speed input and includes a high-pass filter. The proposed combined speed controller is robust against wind measurement errors and as the accuracy of anemometers increases the speed regulation tends toward the ideal controller. The cutoff frequency of the applied filter is determined considering a... 

Artificial neural network (ANN) and genetic algorithm were used in this study to obtain a relatively high flow stress in compression tests for 304 stainless steel. Cold and warm compression were carried out in a temperature range from 20 to 600 °C, strain-rate from 0.001 to 100 S-1 and a strain range from 0.1 to 0.5. Optimum conditions for each case were obtained experimentally and were evaluated by the ANN model. The ANN model was used as fitness function for genetic algorithm. The results indicated that this combined algorithm offers an effective condition for 304 stainless steel, which avoids flow localization, dynamic strain aging, adiabatic shear deformation and void generation. © 2005... 

In this investigation, fine Fe85Si10Ni5 (at.%) powders with a nanocrystalline structure were prepared by high energy ball milling. The effects of milling time on microstructure and magnetic properties of Fe85Si10Ni5 powders were studied by X-ray diffraction (XRD), scanning electron microscope (SEM) and vibrating sample magnetometer (VSM). The optimum soft magnetic properties (maximum saturation magnetization and minimum coercivity) were obtained in alloy powders with an average grain size of 8 nm after 70 h milling. © 2005 Elsevier B.V. All rights reserved  

The synthesis of mono- and bi-supported Ziegler-Natta catalysts using magnesium etoxide Mg(OEt)2 and graphene oxide (GO) as catalyst support for production of Ultra High Molecular Weight Polyethylene (UHMWPE) is reported in this investigation. Nano-graphene oxide was prepared by the modified Hummer's method and its structure was analyzed by XRD and FTIR indicating the presence of hydroxyl groups on graphene oxide and the formation of an exfoliated structure. The activity of TiCl4/Mg(OEt)2, TiCl4/Mg(OEt)2-GO, and TiCl4/GO catalysts in terms of grams of PE produced per mmol of Ti per hour was experimentally obtained for catalysts with different ratios of co-catalyst (triisobutylaluminium) to... 

This article has been devoted to investigation of the tribological properties of ultra-high molecular polyethylene/graphene oxide nanocomposite. The nanocomposite of ultra-high molecular polyethylene/graphene oxide was prepared with 0.5, 1.5, and 2.5 wt% of graphene oxide and with a molecular weight of 3.7 × 106 by in-situ polymerization using Ziegler–Natta catalyst. In this method, graphene oxide was used along with magnesium ethoxide as a novel bi-support of the Ziegler–Natta catalyst. Analyzing the pin-on-disk test, the tribological properties of the nanocomposite, such as wear rate and mean friction coefficient, were investigated under the mentioned contents of graphene oxide. The... 

With increasing the presence of co-and tri-generating units, energy hub operators are encouraged to optimally schedule the available energy resources in an economic way. This scheduling needs to be run in an online manner due to the uncertainties in energy prices and demands. In this paper, the real-time scheduling problem of energy hubs is formulated in a dynamic pricing market. The energy hubs interaction is modeled as an exact potential game to optimize each energy hub’s payments to the electricity and gas utilities, as well as the customers’ satisfaction from energy consumption. The potential game approach enables us to study the existence and uniqueness of the Nash equilibrium (NE) and... 

The authors regret that there were minor errors in the labels of the XRD patterns of cement and micro-silica presented in Figs. 1 and 2, which have been corrected in the figures included here. In addition, due to concerns over the reliability of the XRD pattern of pumice shown in Fig. 9, as caused by a low signal count, the authors have re-analyzed the pumice and the updated XRD pattern has been included here. It is worth noting that these changes do not affect any of the conclusions. The authors would like to apologise for any inconvenience caused. © 2021