Some carbonate rock texture effects on mechanical behavior,based on Koohrang tunnel data,Iran

Bulletin of Engineering Geology and the Environment - The objective of the study described in this paper is to use correlation analysis and multivariate regression analysis for investigating the...     

Application of response surface methodology for optimization of purge gas recycling to an industrial reactor for conversion of CO2 to methanol

Nowadays, by the increasing attention to environment and high rate of fuel production, recycling of purge gas as reactant to a reactor is highly considered. In this study, it is proposed that the purge gases of methanol production unit, which are approximately15.018 t·h~(-1) in the largest methanol production complexes in the world, can be recycled to the reactor and utilized for increasing the production rate. Purge gas streams contain 63% hydrogen,20% carbon monoxide and carbon dioxide as reactants and 17% nitrogen and methane as inert. The recycling effect of beneficial components on methanol production rate has been investigated in this study. Simulation results show that methanol production enhances by recycling just hydrogen, carbon dioxide and carbon monoxide which is an effective configuration among the others. It is named as Desired Recycle Configuration(DRC) in this study. The optimum fraction of returning purge gas is calculated via one dimensional modeling of process and Response Surface Methodology(RSM) is applied to maximize the methanol flow rate and minimize the carbon dioxide flow rate. Simulation results illustrate that methanol flow rate increases by 0.106% in DRC compared to Conventional Recycle Configuration(CRC) which therefore shows the superiority of applying DRC to CRC.     

A fair reader collision avoidance protocol for RFID dense reader environments

A radio frequency identification system can establish a communication between tags and readers through a wireless connection. Due to the optimized coverage of the environment, the readers are placed close to each other in this system and hence it is called dense reader environment. The very property of such an environment leads to increase in the probability of occurrence of reader-to-reader and reader-to-tag collisions which consequently come up with decrease in performance of the network. To solve this problem, many various protocols have been proposed of which centralized ones provide higher throughput. Our proposed method can reduce reader-to-reader collision through combining TDMA and FDMA mechanisms and benefiting from sift probability function and fairness. Furthermore, we found that distance comparison between two readers can reduce reader-to-tag collision as well. Our simulations indicate that the proposed method provides better throughput, average waiting time and fairness than existing ones. Our method also supports the mobility of the readers.     

Modelling of heat transfer and pyrolysis reactions in an industrial ethylene cracking furnace

The development of a relatively simple mechanistic model for an industrial ethylene cracking furnace is described, including the estimation of selected model parameters to improve model predictions. Energy balance equations are developed to account for radiative, conductive, and convective heat transfer in the radiant section, and for convection and conduction in the ultra‐selective heat exchanger (USX) and in the transfer line exchanger (TLE). Kinetic schemes by Ranjan et al. and Sundaram and Froment are used to model the cracking reactions. 1 , 2 The heat transfer model is combined with mass and momentum balances to model gas composition, pressure, and temperature changes as a function of position along the reactor tubes. Initial values and uncertainty ranges are assigned to 44 model parameters based on information in the literature and our industrial sponsor. A sensitivity‐based technique and a mean‐squared‐error (MSE) criterion are used to select the appropriate subset of 22 parameters for tuning. Parameters are estimated and model predictions are validated using industrial data. Model predictions provide a good match to data that were not used for estimation.     

Methodology for developing earthquake‐resilient structures

This paper proposes a methodology for developing earthquake‐resilient structures (ERSs). This is achieved by following principles of full cycle performance control and embracing a holistic approach to design led analysis (DLA) of ERS. Collapse prevention (CP) and postearthquake realignment and repairs (PERRs) are the basic traits of ERS. Despite the availability of several systems involving combinations of gap opening link beams (GOLBs), rigid rocking cores, buckling‐restrained braces, replaceable energy dissipating moment connections, and so forth, neither CP nor PERR are addressed in any code of practice. Although most of these devices have passed several tests of experiments and time–history analysis they have rarely been examined as integral parts of actual buildings. Real buildings cannot be ideally recentered unless specifically designed and detailed for CP and PERR. Almost all simple beam–column joints, especially standard hinged supports absorb small but sufficient amounts of residual strains that hinder PERR. The proposed methodology is introduced by way of developing an earthquake‐resilient rocking core‐moment frame, as the lateral resisting component of a gravity resisting structure that has been detailed not to develop residual effects while sustaining large lateral deformations.