The effect of membrane pores wettability on CO2 removal from CO2/CH4 gaseous mixture using NaOH,MEA and TEA liquid absorbents in hollow fiber membrane contactor

The present paper renders a modeling and a 2D numerical simulation for the removal of CO₂ from CO₂/CH₄ gaseous stream utilizing sodium hydroxide (NaOH), monoethanolamine (MEA) and triethanolamine (TEA) liquid absorbents inside the hollow fiber membrane contactor. Counter-current arrangement of absorbing agents and CO₂/CH₄ gaseous mixture flows are implemented in the modeling and numerical simulation. Non-wetting and partial wetting modes of operation are considered where in the partial wetting mode, CO₂/CH₄ gaseous mixture and liquid absorbents fill the membrane pores. The deteriorated removal of CO₂ in the partial wetting mode of operation is mainly due to the mass transfer resistance imposed by the liquid in the pores of membrane. The validation of numerical simulation is done based on the comparison of simulation results of CO₂ removal using NaOH and experimental data under non-wetting mode of operation. The comparison illustrates a desirable agreement with an average deviation of less than 5%. According to the results, MEA provides higher efficiency for CO₂ removal in comparison with the other liquid absorbents. The order for CO₂ removal performance is MEA > NaOH > TEA. The influence of non-wetting and partial wetting modes of operation on CO₂ removal are evaluated in this article as one of the novelties. Besides, the percentage of CO₂ sequestration as a function of gas velocity for various percentages of membrane pores wetting ranging from 0 (non-wetting mode of operation) to 100% (complete wetting mode of operation) is studied in this research paper, which can be proposed as the other novelty. The results indicate that increase in some operational parameters such as module length, membrane porosity and absorbents concentration encourage the removal percentage of CO₂ from CO₂/CH₄ gaseous mixture while increasing in membrane tortuosity, gas velocity and initial CO₂ concentration has unfavorable influence on the separation efficiency of CO₂.     

Application of Millimeter-Wave Radiometry for Remote Chemical Detection

Passive millimeter-wave systems have been used in the past to remotely map solid targets and to measure low-pressure spectral lines of stratospheric and interstellar gases; however, its application to pressure-broadened spectral line detection of industrial emissions is new. We developed a radiative transfer model to determine feasibility and system requirements for passive millimeter-wave spectral detection of terrestrial gases. We designed and built a Dicke-switched multispectral radiometer in the 146-154-GHz band to detect nitric oxide (NO), a prototypical gas of nuclear fuel processing operations. We first tested the spectral detection capability of the radiometer in the laboratory using a gas cell and then field tested it at the Nevada test site at a distance of 600 m from a stack that released hot plumes of NO and air. With features such as Dicke-switched integration, frequent online calibration, and spectral baseline subtraction, we demonstrated the feasibility of remote detection of terrestrial gases by a ground-based radiometer.     

Semisupervised online learning of hierarchical structures for visual object classification

Multimedia Tools and Applications - One of the main challenges in hierarchical object classification is the derivation of the correct hierarchical structure. The classic way around the problem is...     

Calibration and measurement of dielectric properties of finitethickness composite sheets with open-ended coaxial sensors

The application of open-ended coaxial sensors for dielectric measurement of finite thickness composite sheets is studied. Expressions for calculation of the complex aperture admittance for two geometries are presented. These expressions are used to calculate the dielectric constant of infinite half-space as well as finite thickness slabs. A more efficient method of such calculations, using a personal computer, for low to medium loss dielectrics is demonstrated. The question of when a dielectric layer may be considered as infinitely thick is also addressed, and examples are presented. A different calibration technique (compared to the conventional ones) is described and successfully implemented. This calibration technique utilizes a dielectric sheet with known dielectric properties and thickness. Measurements for different airgaps between the open-ended coaxial line and the dielectric sheet are used to perform and enhance the calibration. The results of this calibration technique and several subsequent measurements are presented and discussed     

Some new efficient multipoint iterative methods for solving nonlinear systems of equations

It is attempted to put forward a new multipoint iterative method of sixth-order convergence for approximating solutions of nonlinear systems of equations. It requires the evaluation of two vector-function and two Jacobian matrices per iteration. Furthermore, we use it as a predictor to derive a general multipoint method. Convergence error analysis, estimating computational complexity, numerical implementation and comparisons are given to verify applicability and validity for the proposed methods.     

Modeling,analysis and multi-objective optimization of twist extrusion process using predictive models and meta-heuristic approaches,based on finite element results

Recently, twist extrusion has found extensive applications as a novel method of severe plastic deformation for grain refining of materials. In this paper, two prominent predictive models, response surface method and artificial neural network (ANN) are employed together with results of finite element simulation to model twist extrusion process. Twist angle, friction factor and ram speed are selected as input variables and imposed effective plastic strain, strain homogeneity and maximum punch force are considered as output parameters. Comparison between results shows that ANN outperforms response surface method in modeling twist extrusion process. In addition, statistical analysis of response surface shows that twist extrusion and friction factor have the most and ram speed has the least effect on output parameters at room temperature. Also, optimization of twist extrusion process was carried out by a combination of neural network model and multi-objective meta-heuristic optimization algorithms. For this reason, three prominent multi-objective algorithms, non-dominated sorting genetic algorithm, strength pareto evolutionary algorithm and multi-objective particle swarm optimization (MOPSO) were utilized. Results showed that MOPSO algorithm has relative superiority over other algorithms to find the optimal points.     

A cloud-based mobile payment system using identity-based signature providing key revocation

The Journal of Supercomputing - Along with the increasing expansion of wireless networks and mobile devices, security, and efficiency in mobile payment systems have become especially important. In...     

Recent advances on akermanite calcium-silicate ceramic for biomedical applications

Owing to great biocompatibility and high capacity of apatite formation, bioceramics, especially calcium silicate-based compounds, were extensively employed in orthopedic and dental uses concerning biomedical applications. Lately, akermanite (AK; Ca₂MgSi₂O₇), as a bioceramic containing Ca-, Mg- and Si, has gained an increased level of attention because of its more tunable mechanical characteristics and degradation rate. All studies indicate that this magnesium incorporating Ca-silicate ceramic has a great capacity to use as a bone graft material to fulfill the necessity of bone reconstruction. Despite the rising interest in using these materials in biomedical fields, there has not yet been an extensive overview of this bioceramic property and its potential benefits. Thus, it has been speculated that this concept and the emergence of akermanite bioactive ceramics might lead to significant upcoming advancements in the field of bone tissue engineering (BTE). Definitely, the approach still requires additional advances to considerably better respond to the vital concerns regarding the clinical application. The review tackles the present research trends on akermanite ceramics for biomedical purposes such as bone scaffold, coating materials, bone cement, and treatment of osteoporotic bone defects, commencing with recent status and shifting to upcoming developments.     

Opportunities for the integration of absorption heat pumps in the pulp and paper process

Implementation of absorption heat pumps (AHPs) in a Kraft pulping process was studied using a new methodology for the optimal integration of those devices in a process. Two generic opportunities were identified for an energy and water optimized mill: (i) integration of a double lift chiller in the bleaching chemical making plant to produce chilled and hot water simultaneously, using MP steam as the driving energy and, (ii) installation of a single stage heat pump to concentrate the black liquor and produce useful hot water by upgrading heat from the bleaching effluent and using MP steam as driving energy. The principles of AHPs operation and their efficient integration into a process are described. The simple payback time (SPB) and net present value (NPV) were used to evaluate the interest of such implementations. Considering 63 $/MWh for the steam price, SPB of 2.7 and 1.7 years have been estimated for the two cases.     

L‐Lysine Monohydrochloride Syrup Concentration using a Membrane Hybrid Process of Ultrafiltration and Vacuum Membrane Distillation

The development of energy saving membrane separation processes is finding a unique position in process industries. One of the important areas where they are employed is the biotechnology industry. This industry has its own specifications and requirements, e.g., levels of diluteness, thermal, chemical and shear fragility. Membrane separation processes have the characteristics necessary to match these specifications and needs. In this research, the determination of the experimental concentration of L‐Lysine monohydrochloride (L‐lysine‐HCl) syrup was investigated using ultrafiltration (UF) and vacuum membrane distillation (VMD) hybrid membrane processes. Four parameters that are known to have significant influence on the UF process were examined, i.e., pressure difference across the membrane, feed concentration of L‐lysine‐HCl, feed velocity on the membrane surface, and pH. For the VMD unit, pressure difference and pH were replaced with feed temperature and vacuum pressure on the permeate side of membrane. Each process was carried out separately and the results were used to design a bench‐scale process. In order to save time and money, the Taguchi method of experimental design was employed. The effects of feed concentration, pressure difference across the membrane, feed velocity on the membrane surface, and pH on the target variable, i.e., the membrane flux, in the UF process were 39.93, 38.65, 9.36, and 9.59 %, respectively. For the VMD process, these values were 64.79, 22.16, 6.21, and 2.14 % for feed temperature, feed concentration, vacuum pressure on the permeate side, and feed velocity on the membrane surface, respectively.