Adsorption characteristics of a fully exchanged potassium chabazite zeolite prepared from decomposition of zeolite Y

In this work a comprehensive study was undertaken to characterize the porous nature of a fully exchanged potassium chabazite zeolite (KCHA) and evaluate its adsorption properties under different conditions. A synthetic chabazite was prepared from the decomposition of zeolite Y and ion-exchanged to produce a fully exchanged potassium chabazite with Si/Al ratio of 2.4. In addition, sodium chabazite (NaCHA) and lithium chabazite (LiCHA) were synthesized for comparison purposes. Equilibrium isotherms for N₂ and CO₂ were measured at 273 K for further characterization. Our results show that the porous structure characterization by N₂ at 77 K and Ar at 87 K following the standard methods of BET for surface area, t-plot, DR and DFT for pore size distribution and volume reveal pore blockage phenomenon with substantially diminished adsorption capacities. However, CO₂ adsorption capacity on KCHA at 273 K reveals magnitudes of 70.1% and 78.7% of those on LiCHA and NaCHA, and a DFT pore volume of 0.214 cm³ g^?1. The surface area of KCHA calculated from the CO₂ isotherm using the Tóth model in its revised form demonstrates a surface area of 584.4 m² g^?1. This is in contrast to 17.82 and 13.48 m² g^?1 obtained from the BET model using N₂ and Ar at 77 and 87 K, respectively. It was concluded that the reliability of standard methods (viz. BET using N₂ at 77 K) for characterizing these particular porous solids is questionable under certain circumstances leading to misevaluation of adsorbent properties.     

Application of an expert system to optimize reservoir performance

The main challenge of oil displacement by an injected fluid, such as in Enhanced Oil Recovery (EOR) processes, is to reduce the cost and improve reservoir performance. An optimization methodology, combined with an economic model, is implemented into an expert system to optimize the net present value of full field development with an EOR process. The approach is automated and combines an economic package and existing numerical reservoir simulators to optimize the design of a selected EOR process using sensitivity analysis. The EOR expert system includes three stages of consultations: (1) select an appropriate EOR process on the basis of the reservoir characteristics, (2) prepare appropriate input data sets to design the selected EOR process using existing numerical simulators, and (3) apply the discounted-cash-flow methods to the optimization of the selected EOR process to find out under what conditions at current oil prices this EOR process might be profitable. The project profitability measures were used as the decision-making variables in an iterative approach to optimize the design of the EOR process. The economic analysis is based on the estimated recovery, residual oil in-place, oil price, and operating costs. Two case studies are presented for two reservoirs that have already been produced to their economic limits and are potential candidates for surfactant/polymer flooding, and carbon-dioxide flooding, respectively, or otherwise subject to abandonment. The effect of several design parameters on the project profitability of these EOR processes was investigated.     

Energy Efficiency Investigation for the MB-OFDM UWB Cross-Layer Design

Green communication has become the main concern of many researchers according to the quick evolution of wireless communication applications. For this, in this correspondence we develop a cross-layer framework based on the joint association between Modulation and Coding Scheme together with truncated Selective Repeat Hybrid Automatic Repeat Request type I to examine the global energy consumption per bit of Multiband Orthogonal Frequency Division Multiplexing Ultra Wideband (MB-OFDM UWB) systems. Indeed, we examine a theoretical analysis based on throughput performance investigation when mode selection is performed which is dynamically selected following the Channel State Information. Next, we prove that cross-layer design outperforms the mode selection behavior in terms of outage probability. Then, based on the features of cross-layer MB-OFDM UWB (MB-UWB) design a theoretical framework is derived in terms of Packet Error Rate and overall energy expenditure per bit. Specifically, the closed form relation of energy per bit is determined by exploiting the proprieties of the two link adaptation tools. Correspondingly, since the purpose behind cross-layer design adoption into MB-UWB system is EE improvement, we have compared the impact of different M-QAM modulations into energy consumption per useful bit at various range of distances. The obtained results reveal that cross-layer design is a powerful solution in terms of EE enhancement.

     

Fuzzy discontinuous term for a second order asymptotic DSMC: An experimental validation on a chemical reactor

In this work, a second order asymptotic discrete sliding mode control with a fuzzy supervised discontinuous term is proposed. The on line variation of the discontinuous term amplitude enhances the convergence rapidity of the sliding function and reduces the chattering phenomenon. These improvements are shown by a numerical simulation and by a real time temperature control of a chemical reactor. Good performances in terms of chattering suppression and reaching phase duration's reduction are noted. Copyright © 2010 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society     

Hierarchical production planning with flexibility in agroalimentary environment: a case study

In this paper we address to the planning problem in the agroalimentary domain. In such industry, several specific constraints should be taken into account for planning task such as the constraints of interdependencies between the products and variable production modes. Furthermore, we present the relationship between two large fields as the production hierarchical planning and the flexibility. Especially, we show that the flexibility planning should be made a priori and then integrated in the hierarchical planning process. Indeed, we have established a mathematical model according to different production levels. While taking into account real capacities of the shop and the interdependencies between the products, the results of our formulation are satisfactory in terms of quality of solution and time requirements. It??s shown that our model is able to reach all optimal solutions for all treated models and for all system levels.     

Plasticized P(VDF-TrFE): A new flexible piezoelectric material with an easier polarization process,promising for biomedical applications

In this work, flexible ferroelectric films of P(VDF-TrFE) softened by a plasticizer are elaborated. Morphology, piezoelectric, mechanical, thermal, and crystalline properties of the films are studied. We show that the elastic constant is reduced up to 30% while increasing the remanent polarization and the piezoelectric coefficient thanks to the lubricant property of the plasticizer, helping the orientation of the crystallites. Plus, the decrease of the coercive field from 46 to 32 V/μm after an annealing at 138°C for a plasticizer content ranging between 20 and 50 wt% is observed and an explanation by based on a polymer/plasticizer demixing is provided. It leads to an easier polarization process with a significant saving in time and applied electric field reducing the breakdown voltage. Both effects could be interesting for an industrial production. Finally, a first sensor is elaborated and characterized electrically with homemade test bench. We show that the softening of the P(VDF-TrFE) offers to the device a larger amplitude range of deformations. The combination of the flexibility with high ferroelectric properties of the plasticized P(VDF-TrFE) make it a very promising material for biomedical sensor applications.     

TCP flow control technique for an interworking interface: hardware implementation

Current TCP flow control depends on packet losses to find the workload that a network can support. A variety of situations, including lossy wireless networks, asymmetric networks and web traffic workload, violates many of the assumptions made by TCP, causing degraded end-to-end performances. To improve the performance of TCP over heterogeneous networks (Ethernet and ATM interconnection), we propose a new technique, which we call Vegas–Snoop+, based on Vegas and Snoop protocols. Two modified service elements take part on the Vegas–Snoop+ technique. First, Vegas service element manages the connection parameters to achieve better throughput. Second, Snoop service element isolates the Ethernet senders from the characteristics of the ATM link. The objective in this paper is to win from advantages of Vegas and Snoop protocols, as well as to search an interconnection interface for networks interoperability. Actually, the development of two new integrated circuits (the BCM5680 (switch) and the BCM5401 (PHY)) orientate researchers to implement, at higher layer of the OSI model, flow control mechanisms to ensure reliability. Vegas–Snoop+ is an implementation of TCP, which gives in this way a solution for traffic management and congestion control improving good throughput with more reliability.     

Experimental study on shear resistance of reactive powder concrete beams without stirrups

Abstract

The tests results of 18 longitudinally reinforced reactive powder concrete (RPC) beams without stirrups and subjected to combined flexural and shear are presented in this paper. The main test variables were the ratio of the shear span-to-effective depth (a/d), the ratio of the longitudinal reinforcement (ρ_w), the percentage of steel fibers volume fractions (V_f) and the percentage of silica fume (SF) powder. The findings of this paper reveal that addition of steel fibers into the RPC mixture does not considerably affect the initial diagonal cracking load but it influences the ultimate load capacity. For all tested fibrous RPC beams, the ratio of the ultimate shear force to diagonal cracking force (V_u∕V_cr) have an average ratio of about 2.5. The shear design equations recommended by the (ACI 318-14) code, (CSA A23.3-04) code, (NZS 3101-06) code and (BS 8110-97) code have been modified to predict the ultimate shear strength of RPC beams without stirrups. The suggested equations gave satisfied predictions for the shear strength of the tested RPC beams with coefficients of variation (COV) ranging from 0.09049 to 0.1817.     

Combinatorial optimization model and MIP formulation for the structural analysis of conditional differential-algebraic systems

In this paper we consider the structural analysis problem for differential-algebraic systems with conditional equations. This problem consists, given a conditional differential-algebraic system, in verifying if the system is structurally nonsingular for every state, and if not in finding a state in which the system is structurally singular. We give a formulation for this problem as an integer linear program. This is based on a transformation of the problem into a matching problem in an auxiliary graph. We also show that the linear relaxation of that formulation can be solved in polynomial time. Using this, we develop a Branch-and-Cut algorithm for solving the problem and present some experimental results.     

Phenolic composition, isolation, and structure of a new deoxyloganic acid derivative from Dhokar and Gemri-Dhokar olive cultivars

Two rare olive cultivars, Dhokar and Gemri-Dhokar, growing in the south of Tunisia were investigated to identify their phenolic profile and evaluate their sugar content and antioxidant activity. The highest value of phenolic content was detected in Gemri-Dhokar cultivar extract (6.97 g gallic acid equivalents/kg of fresh olive). In addition, sugar content was quantified; glucose (45.17 g/kg of fresh olive) was the predominant sugar in Dhokar cultivar, followed by fructose (40.83 g/kg of fresh olive). The identification of phenolic compounds was based on separation by high-performance liquid chromatography equipped with a diode array detector followed by liquid chromatography-mass spectrometry analysis. In both cultivars, Oleuropein aglycon derivatives and elenolic acid were the main phenolic components. Oleuropeins were the major compounds quantified in the Gemri-Dhokar drupes olives (61.04 mg/100 g of fresh olive), while 0.25 mg/100 g were found in fresh Dhokar. A new iridoid compound, isolated as pure compound, was not previously reported in the literature. Its structure was established by spectroscopic analyses (NMR, UV, MS, and IR). DPPH, ABTS, and FRAP assays showed that the most important antioxidant capacity of olive extracts was found in with Gemri-Dhokar cultivar.