Study of Physically Transient Insulating Materials as a Potential Platform for Transient Electronics and Bioelectronics

Controlled degradation and transiency of materials is of significant importance in the design and fabrication of degradable and transient biomedical and electronic devices and platforms. Here, the synthesis of programmable biodegradable and transient insulating polymer films is reported, which have sufficient physical and chemical properties to be used as substrates for the construction of transient electronics. The composite structure can be used as a means to control the dissolution and transiency rate of the polymer composite film. Experimental and computational studies demonstrate that the addition of gelatin or sucrose to a PVA polymer matrix can be used as a means to program and either slow or enhance the transiency of the composite. The dissolution of the polymer composites are fitted with inverse exponential functions of different time constants; the lower time constants are an indication of faster transiency of the polymer composite. The addition of gelatin results in larger time constants, whereas the addition of sucrose generally results in smaller time constants.     

SGDD: self‐managed grid‐based data dissemination protocol for mobile sink in wireless sensor network

The reduction of energy consumption in order to increase network lifetime is one of the most major challenges in the design of wireless sensor networks. During data dissemination, the sensors that are located in the sink's neighborhood are responsible to relay data to the other nodes; hence, their energy is exhausted expeditiously. Therefore, the idea of utilizing mobile sinks can be so advantageous to decrease energy consumption during data dissemination process. In this paper, we propose self‐managed grid‐based data disseminating protocol for mobile sink in wireless sensor networks by using the idea of constructing a virtual grid. In self‐managed grid‐based data disseminating protocol, sink and nodes map their geographical position to a virtual location. In order to increase the performance, we have employed a cell head for each grid cell. Cell heads are selected based on two parameters, centralization and residual energy. Our data dissemination protocol is simple and has low overhead to construct and maintain. Also, we have presented a new method for sink location update, which leads to the least cost in data transfer. Simulation results illustrate that by utilizing hierarchical functionality and determining an optimal size for grid cells, energy consumption is decreased, which leads to increasing network lifetime. Copyright © 2015 John Wiley & Sons, Ltd.     

利用上下文转移实现移动IPv6上的IMS无缝切换

Mobility support for the next generation IPv6 networks has been one of the recent research issues due to the growing demand for wireless services over internet. In the other hand, 3GPP has introduced IP Multimedia Subsystem as the next generation IP based infrastructure for wireless and wired multimedia services. In this paper we present two context transfer mechanisms based on predictive and reactive schemes, to support seamless handover in IMS over Mobile IPv6. Those schemes reduce handover latency by transferring appropriate session ＇information between the old and the new access networks. Moreover, we present two methods for QoS parameters negotiations to preserve service quality along the mobile user movement path. The performances of the proposed mechanisms are evaluated by simulations.     

Platinum‐Coated Hollow Graphene Nanocages as Cathode Used in Lithium‐Oxygen Batteries

One of the formidable challenges facing aprotic lithium‐oxygen (Li‐O₂) batteries is the high charge overpotential, which induces the formation of byproducts, loss in efficiency, and poor cycling performance. Herein, the synthesis of the ultrasmall Pt‐coated hollow graphene nanocages as cathode in Li‐O₂ batteries is reported. The charge voltage plateau can reduce to 3.2 V at the current density of 100 mA g^?1, even maintain below 3.5 V when the current density increased to 500 mA g^?1. The unique hollow graphene nanocages matrix can not only provide numerous nanoscale tri‐phase regions as active sites for efficient oxygen reduction, but also offer sufficient amount of mesoscale pores for rapid oxygen diffusion. Furthermore, with strong atomic‐level oxygen absorption into its subsurface, ultrasmall Pt catalytically serves as the nucleation site for Li₂O₂ growth. The Li₂O₂ is subsequently induced into a favorable form with small size and amorphous state, decomposed more easily during recharge. Meanwhile, the conductive hollow graphene substrate can enhance the catalytic activity of noble metal Pt catalysts due to the graphene‐metal interfacial interaction. Benefiting from the above synergistic effects between the hollow graphene nanocages and the nanosized Pt catalysts, the ultrasmall Pt‐decorated graphene nanocage cathode exhibits enhanced electrochemical performances.     

The influence of steam injection for Enhanced Oil Recovery (EOR) on the quality of crude oil

Currently, due to reduction of oil reservoirs and the increasing need for oil as the main source for world energy, the need for production of heavy oil reservoirs is inevitable. The main purpose of this study is to determine the effectiveness of some operational and reservoir parameters and their impact on thermal and productive efficiency of thermal process of steam injection and quality of crude oil. In order to model the process, Eclipse-300 simulator was employed. Detection of these parameters, in addition to determining the best production scenario, can lead to the use of this method with better economic conditions. Hence, the results obtained from this study show that the optimal values obtained for operational parameters of stream injection such as steam quality, steam injection pressure, injection rate and well completion injection depth. The simulation results show that the use of optimal values of steam injection parameters can enhance efficiency of steam injection method and can make this method considered as third EOR method in heavy oil reservoirs than previously known in the petroleum industry.     

Viscosity estimation of mixed oil using RBF-ANN approach

Diluting the bitumen and heavy oil with a liquid solvent such as tetradecane is one way to decrease the viscosity. The accurate estimation for the viscosity of the aforesaid mixture is serious due to the sensitivity of enhanced oil recovery method. The main aim of this study was to propose an impressive relation between the viscosity of heavy n-alkane and Athabasca bitumen mixtures based on pressure, temperature, and the weight percentage of n-tetradecane using radial basis function artificial neural network (RBF-ANN). Also, this model has been compared with previous equations and its major accuracy was evidenced to estimate the viscosity. The amounts of mean relative error (MRE %) and R-squared received 0.32 and 1.00, respectively. The endeavors confirmed amazing forecasting skill of RBF-ANN for the approximation of the viscosity as a function of temperature, pressure, and the weight percentage of n-tetradecane.     

Kinetic modeling of pyrolysis of three Iranian waste oils in a micro-fluidized bed

Different approaches have been used to convert the waste materials into a clean syngas or other chemicals such as methanol. Among them, pyrolysis is a good candidate to produce the synthesis gas and volatile matters for industrial and refinery applications. In this work, we studied the kinetic and chemical behavior of three Iranian waste oils through a kinetic model and an experimental study. The experiments carried out in a micro-FB reactor, which is a good option for low emissions. Results showed that the reaction temperature and reaction rate are two of the most important factors for maximum conversion level of fuel. Results also showed an optimum value for reaction rate. The modeling results validated against the experimental measurements and found to be in good agreements.     

Prediction of asphaltene precipitation during gas injection

Maintaining the flow of multiphase fluid from the reservoir to the surface has been an important issue with wide economic importance for the petroleum industry. Asphaltene precipitation due to change in temperature, pressure, and composition of oil can adversely affect the oil flow to the surface by reducing the available diameter of the tubing. In this study, the precipitation of asphaltene from an Iranian crude oil was investigated. To do our study, through information about asphaltene instability in the live oil during both natural depletion and gas injection conditions about oil sample from Iranian oil field was gathered. Then, the solid model and scaling model were utilized to predict the weight percent of precipitated asphaltene at a wide range of the pressure and temperature. Results of the work revealed that both models predict the increase in weight percent of precipitated asphaltene when lean gas injected to the live oil at the maximum point of asphaltene instability. In addition, the study showed that both models are capable of predicting the experimental data of asphaltene precipitation; while scaling modeling is more reliable when the gas is injected to the oil.     

Effect of metal loading on catalytic activity and selectivity of ZSM-5 zeolite catalyst in conversion of methanol to olefins and aromatics

Effect of ZSM-5 zeolite promotion using potassium, strontium, and cerium metals on conversion of methanol to light olefins and aromatics was investigated. ZSM-5 catalyst was promoted using wet impregnation of metal salts and its activity was tested in methanol to hydrocarbons process under optimum operational condition obtained in our group previously. Zeolite samples were characterized by X-ray powder diffraction, scanning electron microscopy, N₂ adsorption-desorption, acid sites distribution, and strength using temperature programmed desorption of NH₃. Results showed that presence of these metals could significantly affect acid site distribution and therefore influence the catalyst activity and selectivity to olefins and aromatics.