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Vector space generated by the multiplicative commutators of a division ring
, Article Journal of Algebra and its Applications ; Volume 12, Issue 8 , December , 2013 ; 02194988 (ISSN) ; Akbari, S ; Ariannejad, M ; Madadi, A ; Sharif University of Technology
2013
Abstract
Let D be a division ring with center F. An element of the form xyx -1y-1 ∈ D is called a multiplicative commutator. Let T(D) be the vector space over F generated by all multiplicative commutators in D. In this paper it is shown that if D is algebraic over F and Char(D) = 0, then D = T(D). We conjecture that it is true in general. Among other results it is shown that in characteristic zero if T(D) is algebraic over F, then D is algebraic over F
On-line trace enrichment of phenolic compounds from water using a pyrrole-based polymer as the solid-phase extraction sorbent coupled with high-performance liquid chromatography
, Article Analytica Chimica Acta ; Volume 513, Issue 2 , 2004 , Pages 445-449 ; 00032670 (ISSN) ; Mohammadi, A ; Salemi, A ; Sharif University of Technology
2004
Abstract
A pyrrole-based conductive polymer was prepared and applied as new sorbent for on-line solid-phase extraction (SPE) of phenol and chlorophenols from water samples. Polypyrrole (PPy) was synthesized by chemical oxidation of the monomer in non-aqueous solution. The efficiency of this polymer for extraction of phenol and chlorophenols was evaluated using 35 mg of PPy as the sorbent in an on-line SPE system coupled to reversed-phase liquid chromatography with UV detection. The mobile phase were mixture of phosphate buffer-acetonitrile and compounds were eluted by the mobile phase using a six-port switching valve. High volumes of water, up to 160 ml, could be preconcentrated without the loss of...
Investigation of surface radius variation in design of a lens duct delivery system
, Article Optics and Laser Technology ; Volume 36, Issue 1 , 2004 , Pages 1-10 ; 00303992 (ISSN) ; Sharif University of Technology
2004
Abstract
In this article a ray tracing method is used to study the variation of the entrance and exit surface shape in the different lens ducts systems. Designs with a variety of plane and spherical first and second surfaces are studied. The optimum geometrical conditions for each design in terms of the aperture, length, and the radius of curvature are reported. A comparison is made between the results obtained for ducts with the spherical and plane surfaces and the more efficient design is described. The effect of second-order aspheric shape factor on the device performance is also investigated. This study shows that each design has some advantages and disadvantages, and considering specific...
Simulation of Wave Propagation in the Sea
, M.Sc. Thesis Sharif University of Technology ; Seif, Mohammad Saeed (Supervisor)
Abstract
In positioning and navigation, Sonar with utilization of sound waves in water environments is similar to the role of Radar in not watered (irrigated) environments. In the Sonar field, modeling and simulation of propagation of sound waves in the undersea environment is a fundamental and very important topic. Nowadays simulation is significant tool that allow to the researchers to predict the quality of Sonar function respect to the experimental conditions. For simulation and modeling of sound wave propagation are used two different methods; Wave theory and Ray theory. In the wave theory, because of the large volume of data, the interpretation of the results is hard. Also in this method cannot...
Application of wavefront decomposition to ray tube tracing
, Article MMWaTT 2009 - 1st Conference on Millimeter-Wave and Terahertz Technologies ; 2009 , Pages 5-9 ; 9781424468089 (ISBN) ; Shishegar, A. A ; Sharif University of Technology
Abstract
This paper applies the method of decomposition of wavefronts to ray tube tracing model. Energy ray tubes which are emitted from the source are modeled by three rays and the method of decomposition of wavefronts iteratively improves the accuracy of ray tracing. Comparison with applying the method of decomposition of wavefronts to conventional ray tracing is made afterwards. It is observed that by applying the method of decomposition of wavefronts to ray tube model, the accuracy of ray tracing can be improved much more efficiently and the simulation time decreases to almost a half. ©2009 IEEE
Vectorial Gaussian beam expansion for high-frequency wave propagation
, Article IET Microwaves, Antennas and Propagation ; Volume 4, Issue 12 , 2010 , Pages 2014-2023 ; 17518725 (ISSN) ; Shishegar, A. A ; Sharif University of Technology
Abstract
Wide-waisted Gaussian beam (GB) expansion and point matching methods are discussed in this study as promising techniques for the expansion of electromagnetic waves into GBs. These methods combined with the GB tracing method provide an appropriate scheme for wave propagation analysis in large-scale problems. Details of the wide-waisted GB expansion and point matching methods are provided, and their accuracy and validity regions are discussed. A combination of the aforementioned expansion and tracing methods is utilised to analyse a simple outdoor high-frequency wave propagation problem. The results are compared to the results of the well-known ray tracing method, showing good agreement
Sensitivity analysis of ray tracing to the geometrical description of the environment
, Article IET Microwaves, Antennas and Propagation ; Volume 10, Issue 11 , 2016 , Pages 1225-1234 ; 17518725 (ISSN) ; Shishegar, A. A ; Sharif University of Technology
Institution of Engineering and Technology
Abstract
In ray-tracing-based propagation modelling, the electromagnetic field at the receiver is obtained by coherent summation of the fields of multipath components. It is therefore crucial to accurately calculate the phase of the electromagnetic field of each ray. In practice, when preparing the plan of the environment for ray tracing simulation, the lateral positions of the walls may not be included accurately in the database. This alters the phases of the fields as well as the delays of arrival of multipath components which may consequently lead to less accurate results. In this study, the sensitivity of ray tracing results to this type of geometrical inaccuracy is investigated through the...
Gravity in Noncommutative Geometry
, M.Sc. Thesis Sharif University of Technology ; Esfahani Zadeh, Mostafa (Supervisor)
Abstract
In this thesis, the aim is to stating some of the noncommutative geometry(NCG) applications in formulating and describing the gravity. So, in the first chapter, we will work on some of metric aspects of NCG. In this chapter, we will review elements of the spin geometry, specifically we will define the Dirac operator which is the most important object in this thesis. Then, we will try to find counterparts of some of Riemannian geometric notions like integral and distance in the NCG framework. We will define some notions such as noncommutative infinitesimals, Dixmier trace, Wodzicki residue, noncommutative integral and spectral triples. Then, in the second chapter, we will work on some of the...
Characterization of qutrit channels in terms of their covariance and symmetry properties
, Article Physical Review A - Atomic, Molecular, and Optical Physics ; Volume 84, Issue 1 , July , 2011 ; 10502947 (ISSN) ; Mani, A ; Memarzadeh, L ; Sharif University of Technology
2011
Abstract
We characterize the completely positive trace-preserving maps on qutrits (qutrit channels) according to their covariance and symmetry properties. Both discrete and continuous groups are considered. It is shown how each symmetry group restricts arbitrariness in the parameters of the channel to a very small set. Although the explicit examples are related to qutrit channels, the formalism is sufficiently general to be applied to qudit channels
A new ray tracing acceleration technique based on decomposition of wavefronts
, Article 2008 Asia Pacific Microwave Conference, APMC 2008, Hong Kong, 16 December 2008 through 20 December 2008 ; May , 2008 ; 9781424426423 (ISBN) ; Shishegar, A. A ; Sharif University of Technology
2008
Abstract
A new acceleration technique for the ray tracing algorithm was presented in this paper. Instead of reducing the number of intersection tests, our proposed method finds the solid angles around the transmitter that transport electromagnetic power to the receiver. Then, high-resolution rays are sent out only in these solid angles and the procedure continues iteratively. Since a few rays are traced in each iteration, high resolution can be achieved within acceptable amount of time
A new double counting cancellation technique for three-dimensional ray launching method
, Article IEEE Antennas and Propagation Society International Symposium, APS 2006, Albuquerque, NM, 9 July 2006 through 14 July 2006 ; 2006 , Pages 2185-2188 ; 15223965 (ISSN) ; Shishegar, A. A ; Jedari, E ; Sharif University of Technology
2006
A novel approach to determine minimal tie-sets of complex network
, Article IEEE Transactions on Reliability ; Volume 53, Issue 1 , 2004 , Pages 61-70 ; 00189529 (ISSN) ; Billinton, R ; Munian, T. S ; Vinayagam, B ; Sharif University of Technology
2004
Abstract
Network reliability analysis is usually based on minimal path or cut enumeration from which the associated reliability expressions are deduced. The cut-set method is a popular approach in the reliability analysis of many systems from simple to complex configurations. The computational requirements necessary to determine the minimal cut-sets of a network depend mainly on the number of minimal paths between the source and the sink. A technique designated as the "Path Tracing Algorithm" is presented in this paper, which can handle both simple and complex networks, and considers both unidirectional and bi-directional branches. A step by step procedure is explained using a bridge-network. The...
Coupling of a modified in-tube solid phase microextraction technique with high performance liquid chromatography-fluorescence detection for the ultra-trace determination of polycyclic aromatic hydrocarbons in water samples
, Article Chromatographia ; Volume 59, Issue 7-8 , 2004 , Pages 501-505 ; 00095893 (ISSN) ; Salemi, A ; Sharif University of Technology
Friedr. Vieweg und Sohn Verlags GmbH
2004
Abstract
A modified in-tube solid phase microextraction (SPME) technique in conjunction with a high performance liquid chromatography (HPLC) was developed for the trace determination of polycyclic aromatic hydrocarbons (PAHs) in water samples. The extraction device contained a regular HPLC syringe, replacing the metallic needle by two concentric fused silica capillary tubes. The capillary tubes were coated with polydimethylsiloxane (PDMS) as the sorbent and were attached to the syringe by a homemade interface made from polyether ether ketone (PEEK). The sorption of analytes was achieved by frequent withdrawing and ejecting the water sample from/into a vial via the capillary tubes. For the desorption...
Effects of inaccuracy of material permittivities on ray tracing results for site- Specific indoor propagation modeling
, Article Proceedings of the 2013 IEEE-APS Topical Conference on Antennas and Propagation in Wireless Communications, IEEE APWC 2013 ; Sept , 2013 , Pages 1172-1175 ; 9781467356893 (ISBN) ; Shishegar, A. A ; Sharif University of Technology
IEEE Computer Society
2013
Abstract
The complex dielectric constants of building materials are present in the reflection, transmission and diffraction coefficients of the ray tracing formulation. Any deviation of the dielectric constants included in ray tracing simulation from the actual material properties may be a source of inaccuracy of the simulation results. This paper explores the sensitivity of ray tracing results to the inaccuracy of the dielectric constants of building materials. To do this, the real and imaginary parts of the dielectric constants are considered as random variables to account for the present uncertainty. The propagation of uncertainty in the ray tracing simulation is then obtained by means of the...
Effects of geometrical uncertainties on ray tracing results for site-specific indoor propagation modeling
, Article Proceedings of the 2013 IEEE-APS Topical Conference on Antennas and Propagation in Wireless Communications, IEEE APWC 2013 ; 2013 , Pages 836-839 ; 9781467356893 (ISBN) ; Shishegar, A. A ; Sharif University of Technology
Abstract
The plan of the environment used in a ray tracing simulation is not usually in exact accordance with the actual environment plan. Errors on the order of several centimeters may be present in describing the lateral wall positions. Such errors are comparable to the wavelength in indoor wireless applications and hence, can severely alter the phases of multipath components and lead to inaccurate electromagnetic field at the receiver. In this paper, the impact of this type of geometrical errors on the ray tracing results is investigated. Lateral wall positions are considered as random variables to account for possible geometrical errors. The statistical moments of some channel parameters are...
Indoor ultrawideband propagation modelling using Chebyshev interpolation in 60 GHz band based on ray tracing technique
, Article Conference on Millimeter-Wave and Terahertz Technologies, MMWaTT, 30 December 2014 through 1 January 2015 ; Volume 2015-March , December-January , 2015 ; 21570965 (ISSN) ; 9781479965915 (ISBN) ; Shishegar, A. A ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2015
Abstract
An efficient ray tracing technique for channel modeling of an ultrawideband signal in 60 GHz band is introduced. In the usual method, field calculations at many frequencies must be done where has a high computational cost. We have introduced a novel method using Chebyshev polynomials interpolation to reduce the computational cost. Some propagation parameters such as gain and root mean square (RMS) delay spread are obtained and compared to the other method
Efficient shooting and bouncing ray tracing using decomposition of wavefronts
, Article IET Microwaves, Antennas and Propagation ; Volume 4, Issue 10 , 2010 , Pages 1567-1574 ; 17518725 (ISSN) ; Shishegar, A. A ; Sharif University of Technology
Abstract
A new acceleration technique is presented for shooting and bouncing ray tracing in indoor environments. Tracing just a few rays, the algorithm finds the solid angles around the transmitter that transport electromagnetic power to the receiver. The accuracy is then improved by iteratively increasing the tessellation frequency of the source in the power-transporting solid angles. No rays will be sent through non-power-transporting solid angles, which results in significant reduction of the simulation time. An example of applying the method for studying indoor radio wave propagation is presented and the results are compared with a very high-resolution fully three-dimensional (3D) ray tracing...
A simple and fast solution for fault simulation using approximate parallel critical path tracing
, Article Canadian Journal of Electrical and Computer Engineering ; Volume 43, Issue 2 , 2020 , Pages 100-110 ; Sabaghian Bidgoli, H ; Ghasvari, H ; Hessabi, S ; Sharif University of Technology
IEEE Canada
2020
Abstract
Due to the growing complexity of today's digital circuits, the speed of fault simulation has become increasingly important. Although critical path tracing (CPT) is faster than conventional methods, it is not fast enough for fault simulation of complex circuits with a large number of faults and tests. Exact stem analysis is the most important obstacle in accelerating the CPT method. The simplification of stem analysis eliminates time-consuming computations and makes the CPT method more parallelizable. An approximate and bit-parallel CPT algorithm is proposed for ultrafast fault simulation for both stuck-at-fault (SAF) and transition delay fault (TDF) models. Time linearity, speedup, and...
A performance and functional assertion-based verification methodology at transaction-level
, Article 19th International Conference on Microelectronics, ICM, Cairo, 29 December 2007 through 31 December 2007 ; 2007 , Pages 133-136 ; 9781424418473 (ISBN) ; Gharehbaghi, A. M ; Hessabi, S ; Sharif University of Technology
2007
Abstract
In this paper, we present an assertion-based verification methodology for system-level design. Transactionlevel concepts are integrated with an assertion language to introduce a useful, effective and familiar assertion description language. Our assertion verification language is capable of specifying system-level assertions for validating performance as well as functional properties. Proper-ties can be verified using offline simulation trace analysis. C++ trace checkers are automatically generated to validate particular simulation runs or to analyze their performance characteristic(s). Using a JPEG decoder as a case study, we demonstrate that the assertion-based verification is highly useful...
Indoor Wave Propagation Alanysis Using Modefied Wavefront Decomposition Method
, M.Sc. Thesis Sharif University of Technology ; Shishegar, Amir Ahmad (Supervisor)
Abstract
In recent years, there has been a great studying on site-specific indoor wave propagation mechanism. Conventional ray tracing method is the most common way to predict the profile of the signal in these environments. This method provides us with a deep understanding of signal propagation mechanism including reflection, refraction and diffraction. Knowing these characteristics, we can design a wireless system with optimal performance. Modified Wavefrond Decomposition Method is a ray tracing speed up technique. In this method, a bundle of rays will be traced instead of tracing single rays. If a ray bundle illuminates the receiver location, a ray that exactly crosses the receiver point would be...