2010
42
1
1
61
Calculation for Energy of (111) Surfaces of Palladium in Tight Binding Model
Local Density of States؛ Tight binding Model؛ Surface Energy؛ Recursion Method
2
2
In this work calculation of energetics of transition metal surfaces is presented. The tightbinding model is employed in order to calculate the energetics. The tightbinding basis set is limited to d orbitals which are valid for elements at the end of transition metals series. In our analysis we concentrated on electronic effects at temperature T=0 K, this means that no entropic term will be presented and since we study unrelaxed structures, no elastic deformation contribution will be present either. Density of states is calculated for atoms at the surface and in the bulk for palladium by using the recursion method, when the potential includes only first and second nearest neighbor interactions. The surface energy of fcc (111) surfaces of Pd is also calculated.
1
In this work calculation of energetics of transition metal surfaces is presented. The tightbinding model is employed in order to calculate the energetics. The tightbinding basis set is limited to d orbitals which are valid for elements at the end of transition metals series. In our analysis we concentrated on electronic effects at temperature T=0 K, this means that no entropic term will be presented and since we study unrelaxed structures, no elastic deformation contribution will be present either. Density of states is calculated for atoms at the surface and in the bulk for palladium by using the recursion method, when the potential includes only first and second nearest neighbor interactions. The surface energy of fcc (111) surfaces of Pd is also calculated.
1
4


Ali
Roohforouzi
Iran


Kavoos
Mirabbaszadehii
Iran
Local Density of States
Tight binding Model
Surface energy
Recursion Method
[[1] P. Gambardella, M. Blanc, K. Kuhnke, K. Kern, F. Picaud, C. Ramseyer, C. Girardet, C. Barreteau, D .Spanjaard and M. C .Desjonqueres, Phys. Rev. B 64 045404 (2001) ##[2] S. Rousset, F. Pourmir, J. M. Berroir, J. Klein, J. Lecoeur, P. Hecquet,and B. Salanon, Surf. Sci. 422 (1999) 33 ##[3] J.S. Nelson, P.J. Feibelman, Phys. Rev. Lett. 68 (1992) 2188. ##[4] R. Stumpf, M. Scheffler, Phys. Rev. B 53 (1996) 958. ##[5] P.J. Feibelman, Phys. Rev. B 60 (1999) 11118. ##[6] P.J. Feibelman, Surf. Sci. 463 (2000) L661. ##[7] Z.T. Tian, T.S. Rahman, Phys. Rev. B 47 (1993) 9751. ##[8] R.C. Nelson, T.L. Einstein, S.V. Khare, P.J. Rous, Surf.Sci. 295 (1993) 462. ##[9] K.D. Hammonds, R.M. LyndenBell, Surf. Sci. 298 (1992)437. ##[10] J.W.M. Frenken, P. Stoltze, Phys. Rev. Lett. 82 (1999)3500. ##[11] L. Vitos, H.L. Skriver, J. Kollar, Surf. Sci. 425 (1999) 212. ##[12] M.J. Mehl, D.A. Papaconstantopoulos, Phys. Rev. B 54 (1996) 4519. ##[13] J. Friedel, Physics of Metals, edited by J. M. Ziman ~Cambridge University Press, ambridge, (1969), p. 340 ##[14] M. C. Desjonqueres, D. Spanjaard, Concepts in Surface Physics, SpringerVerlag, Berlin, (1993)##]
Near Pole Polar Diagram of Points and its Duality with Applications
Near Pole Polar Diagram of Points and its Duality with Applications
2
2
In this paper we propose a new approach to plane partitioning with similar features to those of Polar Diagram, but we assume that the pole is close to the sites. The result is a new tessellation of the plane in regions called Near Pole Polar Diagram NPPD. Here we define the (NPPD) of points, the dual and the Contracted dual of it, present an optimal algorithms to draw them and discuss the applications and optimality of the algorithms.
1
In this paper we propose a new approach to plane partitioning with similar features to those of Polar Diagram, but we assume that the pole is close to the sites. The result is a new tessellation of the plane in regions called Near Pole Polar Diagram NPPD. Here we define the (NPPD) of points, the dual and the Contracted dual of it, present an optimal algorithms to draw them and discuss the applications and optimality of the algorithms.
5
10


Bahram
Sadeghi Bighami
Iran


Ali
Mohadesii
Iran
Polar Diagram
Near Pole Polar Diagram
NPPD
Voronoi Diagram
Computational Geometry
Graph Theory
[[1] B. Sadeghi Bigham, A. Mohades, Polar diagram with respect to a near pole, in: 23rd European Workshop on Computational Geometry EWCG07, Austria,206209, 2007. ##[2] C. I. Grima, A. M´arquez and L. Ortega, A new 2D tessellation for angle problems: The polar diagram. Computational Geometry, 34 (2006) 5874. ##[3] B. Sadeghi Bigham, A. Mohades, The Dual of Polar diagrams and its extraction, in: International Conference of Computational Methods in Sciences and Engineering (ICCMSE), Greece, (2006) 451454. ##[4] Zahra Nilforoushan, Ali Mohades, Hyperbolic Voronoi Diagram. ICCSA (5), (2006) 735742. ##[5] C.I. Grima, A. M´arquez, Computational Geometry on Surfaces, Kluwer Academic Publishers, 2001. ##[6] A. Okabe, B. Boots, K. Sugihara, S.N. Chiu, Spatial Tessellations Concepts and Applications of Voronoi Diagrams, second ed., Wiley, Chichester, 2000. ##[7] O. Aichholzer, F. Aurenhammer, D.Z. Chen, D.T. Lee, Skew Voronoi diagrams, Internat. J. Comput. Geometry Appl. 9 (1999) 235247. ##[8] C.I. Grima, A. M´arquez, L. Ortega, A locus approach to angle problems in computational geometry, in: 14th European Workshop in Computational Geometry, Barcelona, Spain, 1998. ##[9] S. Fortune,Voronoi diagrams and Delaunay triangulations, in: D.Z. Du, F.K.Hwang (Eds.), Computing in Euclidean Geometry,World Scientific Publishing, Singapore, 1992, pp. 193233. ##[10] F. Aurenhammer, Voronoi diagrams a survey of a fundamental geometric data structure, ACM Comput. Surveys 23 (1991) 345405. ##[11] B. Aronov, On the geodesic Voronoi diagram of point sites in a simple polygon, Algorithmica 4 (1989) 109140. ##[12] F. Aurenhammer, Power diagramsproperties, algorithms and applications, SIAM J. Comput. 16 (1987) 7896. ##[13] P.F. Ash, E.D. Bolker, Generalized Dirichlet tessellations, Geom. Dedicata 20 (1986) 209243. ##[14] H. Imai, M. Iri, K. Murota, Voronoi diagram in the Laguerre geometry and its applications, SIAM J. Comput. 14 (1985) 93105. ##[15] F. Aurenhammer, H. Edelsbrunner, An optimal algorithm for constructing the weighted Voronoi diagram in the plane, Pattern Recognition 17 (1984) 251257. ##[16] D.T. Lee, Twodimensional Voronoi diagrams in the Lpmetric, J. ACM 27 (1980) 604618.##]
Simulation of Position Based Visual Control and Performance Tests of 6R Robot
Simulation of Position Based Visual Control and Performance Tests of 6R Robot
2
2
This paper presents simulation and experimental results of positionbased visual servoing control process of a 6R robot using 2 fixed cameras. This method has the ability to deal with real time changes in the relative position of the targetobject with respect to robot. Also, greater accuracy and independency of servo control structure from the target pose coordinates are the additional advantages of this method. Forward and inverse kinematics of 6R robot have been simulated then simulation of image processing, object recognition and pose estimation of the end effector as well as targetobject in Cartesian space and visual control of robot have been prescribed. Performance tests of the 6R robot with two cameras have been simulated. Finally, analysis of error and test data has been carried out according to ISO9283, ANSIRIA R15.052 standards and statistical toolbox of MATLAB. Experimental results obtained from actual implementation of visual control and tests of 6R robot in lab are presented and used to validate simulation tests.
1
This paper presents simulation and experimental results of positionbased visual servoing control process of a 6R robot using 2 fixed cameras. This method has the ability to deal with real time changes in the relative position of the targetobject with respect to robot. Also, greater accuracy and independency of servo control structure from the target pose coordinates are the additional advantages of this method. Forward and inverse kinematics of 6R robot have been simulated then simulation of image processing, object recognition and pose estimation of the end effector as well as targetobject in Cartesian space and visual control of robot have been prescribed. Performance tests of the 6R robot with two cameras have been simulated. Finally, analysis of error and test data has been carried out according to ISO9283, ANSIRIA R15.052 standards and statistical toolbox of MATLAB. Experimental results obtained from actual implementation of visual control and tests of 6R robot in lab are presented and used to validate simulation tests.
11
19


M.
Habibnejad Korayem
Iran


A.
Habibnejad Korayem
Iran


F. S.
Heidari
Iran
Position based visual system
performance
test
robot
Simulation
[G. Lopez, C. Sagues and J.J. Guerrero, “HomographyBased Visual Control of Nonholonomic Vehicles”, IEEE Int. Conference on Robotics and Automation, Italy, April 2007. pp. 1703 1708 ##A. Gilbert , M. Giles, G. Flachs , R. Rogers, and H. Yee . “A Real Time Video Tracking Systems.” IEEE , Trans. Pattern Anal. Mech. Intel. 2(1), pp. 47 – 56 Jan. 1983 ##A. C. Sanderson, L. E. Weiss, and C. P. Neuman. Dynamic visual servo control of robots: an adaptive imagebased approach. Proc. IEEE, pages 662.667, 1985. ##M Saedan and M H Ang Jr, “3D VisionBased Control of an Industrial Robot”, Proceedings of the IASTED International Conference on Robotics and Applications, Nov 1922, 2001, Florida, USA, pp. 152157. ##S. Skaar,W. Brockman, and R. Hanson. Cameraspace manipulation. Int. J. Robot. Res., 6(4):20.32, 1987. ##J. T. Feddema, C. S. G. Lee, and O. R. Mitchell. Weighted selection of image features for resolved rate visual feedback control. IEEE Trans. Robot. Autom. 7(1):31.47, February 1991. ##F. Chaumette, P. Rives, and B. Espiau. Positioning of a robot with respect to an object, tracking it and estimating its velocity by visual servoing. In Proc. IEEE Int. Conf. Robotics and Automation, pages 2248.2253, 1991. ##H. Hashimoto, T. Kimoto, T. Ebin, “Manipulator Control with Image Based Visual Servoing” In Proc. IEEE, Conf. Robotics and Automation, pp. 2267 – 2272, 1991. ##M. H. Korayem, N. Shiehbeiki, and T. Khanali, “Design, Manufacturing and Experimental Tests of Prismatic Robot for Assembly Line”, International J. of AMT, Vol. 29, No.34, pp. 379388, 2006. ##M. H. Korayem, K. Khoshhal, A. Aliakbarpour, “Vision Based Robot Simulation and Experiment for Performance Tests of Robot“, International J. of AMT, Vol. 25, No. 1112, pp. 12181231, 2005. ##American National Standard for Industrial Robots and Robot Systems PathRelated and Dynamic Performance Characteristics Evaluation. ANSI/RIA R15.052. 2002. ##ISO9283, “Manipulating Industrial Robots Performance Criteria & Related Test Methods”, 1998. ##D. Koichiro, S. Hironari and U. Shun, “A Goal Oriented JustInTime Visual Servoing for Ball Catching Robot Arm”, IEEE Int. Conference on Robotics and Automation, France, Sep. 2008. pp. 3034 3039. ##]
Markovian Delay PredictionBased Control of Networked Systems
Markovian Delay PredictionBased Control of Networked Systems
2
2
A new Markovbased method for real time prediction of network transmission time delays is introduced. The method considers a MultiLayer Perceptron (MLP) neural model for the transmission network, where the number of neurons in the input layer is minimized so that the required calculations are reduced and the method can be implemented in the realtime. For this purpose, the Markov process order is estimated offline, using prrecorded network time delay history. Unlike most of the previously existing methods, the proposed approach is both accurate and fast enough for a real time implementation. Using such a scheme for realtime estimation of the upcoming time delays, a variable state feedback gain control scheme is also proposed and applied to the predicted discretized model of the plant. The proposed approach is shown, through wellknown benchmark problems, to be both accurate and fast enough for a real time implementation.
1
A new Markovbased method for real time prediction of network transmission time delays is introduced. The method considers a MultiLayer Perceptron (MLP) neural model for the transmission network, where the number of neurons in the input layer is minimized so that the required calculations are reduced and the method can be implemented in the realtime. For this purpose, the Markov process order is estimated offline, using prrecorded network time delay history. Unlike most of the previously existing methods, the proposed approach is both accurate and fast enough for a real time implementation. Using such a scheme for realtime estimation of the upcoming time delays, a variable state feedback gain control scheme is also proposed and applied to the predicted discretized model of the plant. The proposed approach is shown, through wellknown benchmark problems, to be both accurate and fast enough for a real time implementation.
21
28


Behrooz
Rahmani
Iran


Amir H.
D.Markaziii
Iran
Neural Network
Delay Prediction
Entropy
Markov Order Estimation
Networked Control Systems (NCS)
Variable Controller Design
[[1] T.C. Yang, “Networked control system: a brief survey”, IEE Proc.Control Theory Appl., Vol. 153, 2006, pp. 403412. ##[2] W. Zhang, M. S. Branicky, and S. M. Phillips, “Stability of Networked Control Systems”, IEEE Control Systems Magazine, 2001, pp. 8499. ##[3] Y. Tipsuwan and M. Y. Chow, “Control methodologies in networked control systems”, Control Engineering Practice 11, 2003, pp. 1099–1111. ##[4] C. Ma, S. Chen and W. Liu, “Maximum allowable delay bound of networked control systems with multistep delay”, Simulation Modeling Practice and Theory, 2007, pp. 513–520. ##[5] G. P. Liu, Y. Xia, D. Rees, and W. Hu, “Design and Stability Criteria of Networked Predictive Control Systems With Random Network Delay in the Feedback Channel”, IEEE Transaction on Systems, Vol. 37, No. 2, 2007, pp. 173184. ##[6] L. Zhang, Y. Shi, T. Chen, and B. Huang, “A new method for stabilization of networked control systems with random delays”, IEEE Transaction on Automatic Control, 2005, pp. 1177–1181. ##[7] L. Zhang and F. Huajing, “A novel controller design and evaluation for networked control systems with timevariant delays”, Journal of the Franklin Institute, (2006), pp. 161–167. ##[8] L. Zhang and F. Huajing, “Fuzzy controller design for networked control system with timevariant delays”, Journal of Systems Engineering and Electronics, Vol.17, No. 1, 2006, pp.172– 176. ##[9] J. Yi, Q. Wang, D. Zhao and J. T. Wen, “BP neural network predictionbased variableperiod sampling approach for networked control systems”, Applied Mathematics and Computation, 2006, pp. 976–988. ##[10] Zhang, L., Shi, Y., Chen, T., and Huang, B., “A new method for stabilization of networked control systems with random delays, IEEE TRANSACTIONS ON AUTOMATIC CONTROL, Vol. 50, 2005, pp. 1177–1181. ##[11] Q.P. Wang, D.L. Tan, Ning Xi, Y.C. Wang, “The Control Oriented QoS: Analysis and Prediction”, Proceedings of the 2001, IEEE International Conference on Robotics 8 Automation. ##[12] North, S. Sahin, F., "Picasso: realtime estimation of network delay over a telerobotic link", IEEE International Conference on Systems, Man and Cybernetics, 2002. ##[13] S. Soucek and G. koler, “Impact of QOS parameter on InternetBased EIA709.1 Control Applications”, IEEE Conference Proceeding, USA, Vol. 4, 2002, pp. 31763181. ##[14] N. N. R. Ranga Suri, D. Deodhare and P. Nagabhushan, “Parallel Levenberg Marquardtbased Neural Network Training on Linux Clusters  A Case Study”, Proceedings of the Third Indian Conference on Computer Vision, Graphics & Image Processing, India, 2002. ##[15] S. Miller and D. Childers, Probability and Random Processes: With Applications to Signal Processing and Communications, Academic Press, 2004. ##[16] S. U. Pillai and A. Papoulis, Probability, Random Variables, and Stochastic Processes, McGrawHill, 2002. ##[17] H. Kong and E. Shwedyk, “A Measure for the Length of Probabilistic Dependence”, IEEE, ISlT, Ulm, Germany, 1997, pp. 469. ##[18] T. M. Cover and J. A. Thomas, Elements of Information Theory, WileyInterscience, 1991. ##[19] K. J. Astrom (Author), and B. Wittenmark, ComputerControlled Systems: Theory and Design, Prentice Hall; 3 edition, Nov 20 1996. ##[20] J. Xiong and J. Lam, “Stabilization of Networked Control Systems with a Logic ZOH”, IEEE TRANSACTIONS ON AUTOMATIC CONTROL, VOL. 54, NO. 2, FEBRUARY 2009. ##]
Mechanism of Improvement of Formability in Pulsating Hydroforming of Tshape Tubes
Mechanism of Improvement of Formability in Pulsating Hydroforming of Tshape Tubes
2
2
In this paper, the mechanism of improvement of formability in pulsating hydroforming of Tshape tubes is investigated by the finite element simulation and experiment. It is shown that local thinning was prevented by oscillating the internal pressure, because the protrusion is formed gradually by the prevention of sharp bulging. In the hydroforming, for the pulsating pressure, several steps occur in variations in wall thickness, and thus, the thickness of the tube increases; whereas, for the peak pressure, the thickness is reduced continuously. Moreover, the effects of the amplitude and the number of cycles of pressure per unit punch, the stroke on formability and the corner filling are examined. It is shown that the small number of cycles of pressure and large amplitudes improve the formability; whereas, a large number of cycles of pressure and small amplitudes increase the die corner filling and shape accuracy as well.
1
In this paper, the mechanism of improvement of formability in pulsating hydroforming of Tshape tubes is investigated by the finite element simulation and experiment. It is shown that local thinning was prevented by oscillating the internal pressure, because the protrusion is formed gradually by the prevention of sharp bulging. In the hydroforming, for the pulsating pressure, several steps occur in variations in wall thickness, and thus, the thickness of the tube increases; whereas, for the peak pressure, the thickness is reduced continuously. Moreover, the effects of the amplitude and the number of cycles of pressure per unit punch, the stroke on formability and the corner filling are examined. It is shown that the small number of cycles of pressure and large amplitudes improve the formability; whereas, a large number of cycles of pressure and small amplitudes increase the die corner filling and shape accuracy as well.
29
35


M.
LohMousavii
Iran


M.
BakhshiJooybariii
Iran


K.
Moriiii
Iran
Tube hydroforming
Pulsating hydroforming
Tshape tubes
FE Simulation
Tube formability
[[1] S. J. Kang, H. K. Kim, B. S. Kang, "Tube size effect on hydroforming formability", J. Mater. Process. Technol., Vol. 160, pp. 2433, 2005. ##[2] M. Strano, S. Jirathearanat, S. G. Shr, T. Altan, "Virtual process development in tube hydroforming", J. Mater. Process. Technol., Vol. 146, pp. 130136, 2004. ##[3] http://www.opton.co.jp ##[4] Mori, K., Patwari, A.U., Maki, S., "Improvment of formability by oscillation of internal pressure in pulsating hydroforming of tubes", Ann. CIRP, Vol. 53, No. 1, pp. 215218, 2004. ##[5] K. Mori, T. Maeno, S. Maki, "Mechanism of improvement of formability in pulsating hydroforming of tube", Int. J. of Mach. Tools and Manu. 47, pp. 978984, 2007. ##[6] T. Hama, M. Asakawa, H. Fukiharu, A. Makinouchi, M., "Finite Element Simulation of Hammering Hydroforming of an Automotive Component", in Proc. TUBEHYDRO2003, Aichi, Japan, pp. 8083. ##[7] M. LohMousavi, K. Mori, K. Hayashi, S. Maki, M. Bakhshi, "3D finite element simulation of pulsating Tshape hydroforming of tubes", Key Engineering Materials, vol. 340, pp. 353358, 2007. ##[8] M. LohMousavi, K. Mori, K. Hayashi and M. Bakhshi, "Improvement of filling of die corners in boxshaped tube hydroforming by control of wrinkling", Key Engineering Materials, vol. 344, pp. 461467, 2007. ##[9] M. Suetake, K. Manabe, S. Miyamoto, H. Koyama, T. Yagami, M. Yang, "Development of tube hydroforming with intelligent process control system", in Proc. TUBEHYDRO 2003, Aichi, Japan, pp. 714. ##[10] G.T. Kridli, L. Bao, P. K. Mallick, Y. Tian, "Investigation of thickness variation and corner filling in tube hydroforming", J. Mater. Process. Technol., Vol. 133, pp. 287296, 2003. ##[11] K. Mori, T. Maeno, M. BakhshiJooybari, S. Maki, "Measurment of friction force in free pulsating hydroforming", Advanced Technology of Plasticity 2005, Padova, CDROM. ##]
A Theoretical and Experimental Study of Failure Maps of Sandwich Beams with Composite Skins and Honeycomb Core
A Theoretical and Experimental Study of Failure Maps of Sandwich Beams with Composite Skins and Honeycomb Core
2
2
Failure maps of sandwich panels such as beam, plate and shell are of great importance in designing such structures. In this paper, failure maps of sandwich beams with composite skin and honeycomb core are obtained. The effect of transverse shear in skins and core and the effect of double walls of honeycomb core have been taken into account. Shear deformation of skins and core are assumed to be linear. By minimizing the potential energy equation, the shear deformation coefficients of core and skins are obtained. Axial stresses in skins and core are obtained in terms of these coefficients. Core is assumed to have orthotropic properties. Three point bending tests have been performed on some sandwich beam specimens. It is found that specimens for which failure load and its corresponding failure mode lie away from the boundary lines in failure map, there is a little difference between failure loads obtained from theories and experiments but this difference is more significant near the boundary lines due to combination of failure modes. In the case of transverse ribbon direction, the theoretical and experimental results are closer.
1
Failure maps of sandwich panels such as beam, plate and shell are of great importance in designing such structures. In this paper, failure maps of sandwich beams with composite skin and honeycomb core are obtained. The effect of transverse shear in skins and core and the effect of double walls of honeycomb core have been taken into account. Shear deformation of skins and core are assumed to be linear. By minimizing the potential energy equation, the shear deformation coefficients of core and skins are obtained. Axial stresses in skins and core are obtained in terms of these coefficients. Core is assumed to have orthotropic properties. Three point bending tests have been performed on some sandwich beam specimens. It is found that specimens for which failure load and its corresponding failure mode lie away from the boundary lines in failure map, there is a little difference between failure loads obtained from theories and experiments but this difference is more significant near the boundary lines due to combination of failure modes. In the case of transverse ribbon direction, the theoretical and experimental results are closer.
37
47


M.
Sadighi
Iran


A. A.
Dehkordi
Iran


R.
Khodambashi
Iran
Sandwich beam
failure maps
Honeycomb
composite skins and transverse shear stress
[[1] Allen HG. Analysis and design of structural sandwich panels.London: Pergamon Press, 1969. ##[2] Holt PJ, Webber JPH. Exact solutions to some honeycomb beam, plate and shell problems. Journal of Strain Analysis 1982; 17( I ): l8. ##[3] Gibson LJ, Ashby MF. Cellular solids: structure and properties. 2nd ed. Cambridge, UK: CambridgeUniversity Press; 1997. ##[4] Masters IG, Evans KE. Models for the elastic deformation of honeycombs. Compos Struct 1996;35:403–22. ##[5] Mukhopadhyay AK, Sierakowski RL. On sandwich beams with laminated facings and honeycomb cores subjected to hygrothermal loads: Part I. Analysis. Journal of Composite Materials1990;244:382400. ##[6] Wierzbicki T, Abramowizc W. On the crashing mechanics of thinwalled structures. J Appl Mech 1983;50:727–39. ##[7] Abramowizc W, Jones N. Dynamic axial crashing of square tubes. Int J Impact Eng 1984;2:263–81. ##[8] Zhang J, Ashby MF. The outofplane properties of honeycomb. Int J Mech Sci 1992;34(6):475–89. ##[9] Zhang J. The mechanics of foams and honeycombs, PhD thesis, University of Cambridge, United Kingdom, 1989. ##[10] Wu E, Jiang WS. Axial crush of metallic honeycomb. Int J Impact Eng 1997;9(5–6):439–56. ##[11] Gotoh M, Yamashita M, Kawakita A. Crush behaviour of honeycomb structure impacted by drophammer and its numerical analysis. Mater Sci Res Int 1996;2(4):261–6. ##[12] Yasui Y. Dynamic axial crushing of multilayer honeycomb panels and impact tensile behaviour of the component members. Int J Impact Eng 2000;24:659–71. ##[13] Paik JK, Thayamballi AK, Kim GS. The strength characteristics of aluminium honeycomb sandwich panels. ThinWalled Struct 1999;35:205–31. ##[14] Zhao H, Gary G. Crushing behaviour of aluminium honeycombs under impact loading. Int J Impact Eng 1998;21(10):827–36. ##[15] Baker WE, Togami TC, Weydert JC. Static and dynamic properties of highdensity metal. Int J Impact Eng 1998;21(3):149–63. ##[16] Wierzbicki T. Crushing analysis of metal honeycombs. Int J Impact Eng 1983;1(2):157–74. ##[17] Shenhar Y, Frostig Y, Altus E. Stresses and failure patterns in the bending of sandwich beams with transversely flexible cores and laminated composite skins. Composite Structures 1996;35: 143 152. ##[18] Triantafillou TC, Gibson LJ. Failure mode maps for foam core sandwich beams. Materials Science and Engineering 1987; 95:3753. ##[19] A. Petras, M.P.F. Sutcliffe. Failure mode maps for honeycomb sandwich panels. Composite Structures 44 (1999) 237252. ##[20] Ciba Composites, Duxford, England, Honeycomb Sandwich Design Technology. August 1995. ##[21] Anonymous, Method of flexure tests of flat sandwich structures. ASTM, 15.03 (C39362) 1989.##]
Heat Transfer Characteristics of Porous Radiant Burners Using DiscreteOrdinate Method (S2Approximation)
Heat Transfer Characteristics of Porous Radiant Burners Using DiscreteOrdinate Method (S2Approximation)
2
2
This paper describes a theoretical study to investigate the heat transfer characteristics of porous radiant burners. A one dimensional model is used to solve the governing equations for porous medium and gas flow before the premixed flame to the exhaust gas. Combustion in the porous medium is modeled as a spatially dependent heat generation zone. The homogeneous porous media, in addition to its convective heat exchange with the gas, may absorb, emit and scatter thermal radiation. The radiation effect in the gas flow is neglected but the conductive heat transfer is considered. In order to analyze the thermal characteristics of porous burners, the coupled energy equations for the gas and porous medium based on the discrete ordinate method are solved numerically and the effect of various parameters on the performance of porous radiant burners are examined. Comparison between the present results with those obtained by other investigators shows a good agreement.
1
This paper describes a theoretical study to investigate the heat transfer characteristics of porous radiant burners. A one dimensional model is used to solve the governing equations for porous medium and gas flow before the premixed flame to the exhaust gas. Combustion in the porous medium is modeled as a spatially dependent heat generation zone. The homogeneous porous media, in addition to its convective heat exchange with the gas, may absorb, emit and scatter thermal radiation. The radiation effect in the gas flow is neglected but the conductive heat transfer is considered. In order to analyze the thermal characteristics of porous burners, the coupled energy equations for the gas and porous medium based on the discrete ordinate method are solved numerically and the effect of various parameters on the performance of porous radiant burners are examined. Comparison between the present results with those obtained by other investigators shows a good agreement.
49
59


M. M.
Keshtkari
Iran


S. A
. Gandjalikhan Nassab
Iran
porous radiant burners
discrete ordinate method
radiative transfer
thermal characteristics
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Effects of Influence Parameters on Color Formation in Glucose Syrups during Storage
Effects of Influence Parameters on Color Formation in Glucose Syrups during Storage
2
2
Effects of pH, temperature, and syrup concentration on color formation in glucose syrups were studied and the shelf life of syrups under various conditions was estimated. Temperatures of 5, 25, and 45 ºC, pH values of 4, 5, and 6 as well as concentrations of 30, 40, 50, 60, 70, and 80 ºBrix were examined. After 26 weeks no significant color changes were observed at 5 ºC. At 45 ºC, color formation rate was highest and after 2 weeks color changes were visible, and at 15th week syrup color was completely brown. At 25 ºC, color formation rate was low and at week 18 color changes were visible. At pH 5, rate of browning was lower than at other pH values. Increasing the syrup concentration up to 70 ºBrix enhanced the color formation rate but higher concentrations decreased the color formation rate. The kinetics of color formation was studied and rate constants and activation energies were calculated.
1
Effects of pH, temperature, and syrup concentration on color formation in glucose syrups were studied and the shelf life of syrups under various conditions was estimated. Temperatures of 5, 25, and 45 ºC, pH values of 4, 5, and 6 as well as concentrations of 30, 40, 50, 60, 70, and 80 ºBrix were examined. After 26 weeks no significant color changes were observed at 5 ºC. At 45 ºC, color formation rate was highest and after 2 weeks color changes were visible, and at 15th week syrup color was completely brown. At 25 ºC, color formation rate was low and at week 18 color changes were visible. At pH 5, rate of browning was lower than at other pH values. Increasing the syrup concentration up to 70 ºBrix enhanced the color formation rate but higher concentrations decreased the color formation rate. The kinetics of color formation was studied and rate constants and activation energies were calculated.
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Ahmadreza
Raisii
Iran


Abdolreza
Aroujalianii
Iran
Glucose syrups
Browning
Maillard reaction
Reaction kinetic
Shelf life
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