Synthesis of modified catalyst and stabilization of CuO/NH4‐ZSM‐5 for conversion of methanol to gasoline

In this article, the catalytic conversion of methanol to gasoline range hydrocarbons has been studied over CuO/ NH₄‐ZSM‐5(3,5,7,9%) catalysts prepared via sono‐chemistry methods. In order to improve, copper oxide can be used as a booster on NH₄‐ZSM‐5 this catalyst property. Accordingly, the conversion process of Methanol to Gasoline (MTG) was conducted under a pressure of 1 atm and temperature of 400°C by a fixed‐bed reactor on copper oxide catalysts which were prepared based on synthetic NH₄‐ZSM‐5. The synthetic catalyst was investigated by such analyses as BET, XRD, FT‐IR, and SEM. Formation of copper oxide phase and proper distribution of copper oxide were proven on the basic level of using XRD analysis. BET analysis showed the reduction in catalyst level and SEM images depicted the proper distribution of particles. The present investigation is to study the effect of CuO loading on NH4‐ZSM‐5 support for conversion of methanol to gasoline range hydrocarbons. A series of CuO/ NH4‐ZSM‐5 catalysts were prepared, characterized, and experimented for their performance on methanol conversion and hydrocarbon yield.     

Graph products for configuration processing of space structures

In this paper four undirected graph products and four directed graph products are presented for the formation of structural models. The undirected products are extensively used in graph theory and combinatorial optimization, however, the directed products defined in this paper are more suitable for the formation of practical structural models. Here, the directed and undirected products are employed for the configuration processing of space structures. This application can easily be extended to the formation of finite element models.     

Exploitation of symmetry in graphs with applications to finite and boundary elements analysis

We present explicit and parametric forms of transformation matrices for three well‐known and widely used symmetry groups: S₂, C_2v and C_4v. Group representation theory is the most powerful method for exploiting symmetry. We propose an efficient algorithm for systematic generation of reducible representations that can be combined linearly to obtain the projection operators. The exact column spaces of these projection operators are calculated and integrated through special orderings, leading to exact explicit and parametric forms of transformation matrices. The transformation matrices could be used directly for block diagonalization of single‐variable scalar field problems. Another algorithm is proposed to extend the application of the method to nonscalar and multivariable field problems. Finally, the generality and efficiency of the proposed method in relation to computation times and the accuracy of results are illustrated through examples from spectral decomposition, free vibration, buckling of FEMs and boundary element analysis of a symmetric field. Copyright © 2012 John Wiley & Sons, Ltd.     

Design and construction of Alborz tokamak vacuum vessel system

The Alborz tokamak is a D-shape cross section tokamak that is under construction in Amirkabir University of Technology. At the heart of the tokamak is the vacuum vessel and limiter which collectively are referred to as the vacuum vessel system. As one of the key components for the device, the vacuum vessel can provide ultra-high vacuum and clean environment for the plasma operation. The VV systems need upper and lower vertical ports, horizontal ports and oblique ports for diagnostics, vacuum pumping, gas puffing, and maintenance accesses. A limiter is a solid surface which defines the edge of the plasma and designed to protect the wall from the plasma, localizes the plasma–surface interaction and localizes the particle recycling. Basic structure analyses were confirmed by FEM model for dead weight, vacuum pressure and plasma disruptions loads. Stresses at general part of the VV body are lower than the structure material allowable stress (117 MPa) and this analysis show that the maximum stresses occur near the gravity support, and is about 98 MPa.     

STABILITY PREDICTION OF TITANIUM MILLING WITH DATA DRIVEN RECONSTRUCTION OF PHASE-SPACE

Significant research effort has been carried out in the detection of chatter, which is one of the main barriers against titanium milling. State-of-the-art techniques are unable to satisfy requirements of industry in terms of in-process chatter detection. The present study reports the use of sensor-signal driven reconstructed phase space attractors combined with image correlation as a solution of chatter prediction during milling of titanium in industry. The method uses Poincaré sections of reconstructed phase space attractor as patterns to identify the onset of chatter in the apparently random behavior of vibrations in the milling process. Image correlation of Poincaré sections indicates the onset of chatter in the milling process.     

Frequency Range Determination for Reflectometry System in Alborz Tokamak Using 2D FDTD Simulation

Reflectometry is a plasma diagnostic technique similar to radar. Microwaves are lunched into the plasma and reflected at the critical surfaces. By receiving the reflected microwave signals and comparing them with the lunched waves, the plasma density profile and its fluctuations can be obtained. Multiple-fixed-frequency reflectometry is one of the methods which considered determining Alborz Tokamak plasma cut off layers position and plasma density profile. In order to design components of the reflectometer, the main parameter which should exactly be determined, is the range of microwave frequency. For the mentioned purpose, a 2D code is used to simulate plasma profile reconstruction in Alborz Tokamak. The code uses the finite-difference-time-domain method with a perfectly-matched-layer absorption boundary to solve Maxwell’s equations. A 1D formula also is used to verify values resulted from the simulation. The good agreement between calculated and simulated values shows the high accuracy of the simulation. With respect to the simulation results, the appropriate range of frequency is determined and the reflectometer components can be designed according to this frequency range.     

A new compact dual‐wideband printed monopole antenna for WLAN/WiMAX applications

A new compact printed monopole antenna with dual‐wideband characteristics is presented for simultaneously satisfying wireless local area network and worldwide interoperability for microwave access applications. The antenna structure consists of a circular monopole with a microstrip feed‐line for excitation and a hexagon conductor‐backed parasitic plane. The antenna has a small size of 13 mm × 26 mm × 1 mm. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.     

Combinatorial optimization of special graphs for nodal ordering and graph partitioning

There are numerous applications of graph theory and algebraic graph theory in combinatorial optimization and optimal structural analysis. In this paper, a new canonical form as well as its relation with four structural models often encountered in practice and their corresponding graphs are presented. Furthermore, the block diagonalization of this form, which is performed using three Kronecker products and unsymmetric matrices, is studied. This block diagonalization leads to an efficient method for the eigensolution of adjacency and Laplacian matrices of special graphs. The eigenvalues and eigenvectors are used for efficient nodal ordering and partitioning of large structural models. The present method is far more simple than any existing general approach.     

Very ultra-wideband printed CPW-fed slot antenna

A very ultra-wideband compact microstrip slot antenna targeting the 3.1-10.6-GHz frequency band is presented. The proposed antenna is a simple printed slot antenna with a novel radiator, which is fed by a 50 Omega CPW line. The measured return loss extends from 2.8-33.4-GHz, about 169-. The proposed antenna has a compact size of 24-25-mm. The measured radiation patterns confirm that the antenna shows an approximately omnidirectional radiation pattern.     

Design,Simulation and Construction of a Low-Density Fixed-Frequency Refleloctometer

Since some tokamaks such as Taban are currently working with low density plasma, a fixed frequency reflectometer system was designed and constructed to monitor plasma production within the vacuum vessel. In this paper, the detail of design, simulation and construction of the system is presented. Moreover, some experiments which have been made for the evaluation of the system performance is reported. The system consists of a circular waveguide-antenna to both transmit and receive the microwave as well as a fully integrated system for measuring the phase difference between transmitted and received signals. To make sure of the perfect performance of the constructed system, some experiments were conducted to individually evaluate system operation. In order to verify the obtained results, all the mentioned experiments were simulated using CST software and the simulation results were compared with those obtained from the experiments. Good agreements were observed between simulation and experimental results, implying the high reliability of the system operation. After approval of the system performance, the system was implemented in Taban Tokamak to monitor the plasma production. Using the reflectometer outputs, the plasma density was estimated.