Proceedings of the 8th WSEAS International Conference on SIGNAL PROCESSING, ROBOTICS and AUTOMATION Matrix inverse operation convolution: Three Models description. JESUS MEDEL Research Center of Applied Science and Advance Technology and Research Center for Computing, National Polytechnic Institute IPN, Av. Juan de Dios Batiz s/n, Edificio CIC Col. Nueva Industrial Vallejo, 07738 Mexico City MEXICO [email protected] CONSUELO V. GARCIA Research Center of Applied Science and Advance Technology, National Polytechnic Institute IPN, Legaria No. 694 Col. Irrigación, 11500 Mexico City MEXICO [email protected] Abstract: This paper gives a short introduction and a description that defines the basic inverse convolution operation structure and explains with short comments some of its applications in astronomy, microscopy and analysis of seismic measures. The second part presents formal convolution and inverse convolution operation concepts about various issues concerned: The first correspond to convolution as a matrix expands expression, which provides the necessary preamble to define the three models respect to inverse convolution operation Matrix suggested in this work. Requiring in probability manner the MSE (Mean Square Error), either the diagrams Decibels description into the proposed inverse convolution models operation in simulation graphs. Finally, it shows in which of the three inverse convolutions operation methods simulated was the best convergence rate. Graphically speaking compared the inverse convolution operation signals respect to original signal before convolutioned. The convergence error functional was obtained respect to MSE, using the second probability moment and Decibels expression in recursive form. Analyzing the simulation results, could be concluded that the optimal inverse convolution operation was the good enough estimation methods, respect to the last two methods considered. Key-Words: Inverse convolution operation, error functional, estimation, filtering, identification, recursive decibels. 1 Introduction reconstruction process 16, or the blind inverse convolution operation in astronomy, which in turn improved an initial identification of the real object reaching a certain predetermined criteria 1, 16 and [18]. The analysis of the earthquake required using a division spectral method [2] and [14], or in digitalized systems. In the last ten years was considered the discrete wavelet packet transform as good enough tools into inverse convolution operation 11, [12] and [13]; but didn`t compare with other previous techniques. The problem of recovering an original signal, after being convolution process was treated with different methods 1,2, 6, 7, 12, 16 and [17]; for example: inverse convolution operation, homomorphic inverse convolution operation, online or iterative inverse convolution operation 2, with intelligent computational structures 1, and identification systems techniques 16 , in the others. All of its minimizing the MSE respect to original signal. The inverse convolution operation is either a mathematical operation as a signal restoration for to recover data degraded by someone physical process interacting 2. This operation has a lot of applications into the earthquake analysis; microscopy and astronomy, reserving in each case the resolution of inverse convolution operation, treating as a complex problem 6 and 7. For example, used in iterative algorithms, obtaining the maximum likelihood estimation in microscopy, in the others sciences, which concerns itself with the identification in the ISSN: 1790-5117 2 Convolution Operations Convolutions in discrete form could be described as a basic inner point operation respect two signals, each of its delayed (basic signal) respect to the others, generally the last of its perturbing the original natural data signal evolution 8 and [13]. 246 ISBN: 978-960-474-054-3 Proceedings of the 8th WSEAS International Conference on SIGNAL PROCESSING, ROBOTICS and AUTOMATION Theorem 1: The discrete convolution operation after all delayed could be seeing as an expanded matrix results: (1) 𝐶𝑚𝑥 1 = 𝐺𝑚𝑥𝑛 𝐹𝑛𝑥 1 . operation as a unique signal 𝐶𝑚 ×1 compounded by a matrix with rows enlarged 𝐺𝑚 ×𝑛 ; and unknowing the fix expanded vector 𝐹𝑚 ×1 . Theorem 2: The inverse convolution operation required for to find the known fix expanded vector 𝐹𝑚 ×1 , considering that 𝐺𝑚 ×𝑚 is a simple square matrix and not singular, is given: (7) 𝐹𝑚 ×1 = 𝐺𝑚 ×𝑚 −1 𝐶𝑚×1 . Where the convolution matrix 𝐶𝑚𝑥 1 , is the inner product between the matrix with rows enlarged knowing symbolically as 𝐺𝑚𝑥𝑛 (conformed its by a vector set displaced each time intervals and representing within the enlarged single parent displacement columns referring to each time period considered within convolution matrix) and the fixed signal 𝐹𝑛𝑥 1 . Proof (Direct form). Observing that the convolution theorem expression by square matrix condition expressed in (1), and in agreement the concepts considered in 4 and 8, the final results has the essential form (7) ■ . Proof (Inductive technique). Symbolically speaking 2 and 8, the convolution between two signals: Theorem 3: The inverse convolution vector operation for 𝐹𝑚 ×1 , with no square matrix 𝐺𝑚 ×𝑛 is: (8) 𝐹𝑛𝑥 1 = 𝐺′𝑛×𝑚 𝐺𝑚×𝑛 + 𝐺′𝑛×𝑚 𝐶𝑚 ×1 . +∞ 𝑐 𝑡 = 𝑔 𝑡 − 𝑥 𝑓 𝑥 𝑑𝑥 . (2) −∞ As a discrete approximation using finite differences 3, for each time, the convolution by t1 𝐶1 = 𝐶(𝑡1 ) = 𝑛𝑥=1 𝐺 𝑡1 − 𝑥 𝐹 𝑥 . So that 𝐶1 = 𝐺 𝑡1 − 𝑥 , 𝐹 𝑥 Proof (Direct form). Given the convolution expression (1) and, being a rectangular matrix 𝐺𝑚 ×𝑛 , right multiplying both sides of initial equation by its transposed, finding a square matrix: (9) 𝐺′𝑛×𝑚 𝐶𝑚×1 = 𝐺′𝑛×𝑚 𝐺𝑚×𝑛 𝐹𝑛×1 . (3) So that det (𝐺′𝑛×𝑚 𝐺𝑚 ×𝑛 ) = 0, could be obtained its pseudoinverse [18] and [21] as an approximation describing the fix vector 𝐹𝑛×1 depicted in (8) ■ . Now, the convolution operation by t2 𝐶2 = 𝐶 𝑡2 = 𝑛 𝑥=1 𝐺 𝑡2 − 𝑥 𝐹 𝑥 . So that 𝐶2 = 𝐺 𝑡2 − 𝑥 , 𝐹 𝑥 And so on to tm, 𝐶𝑚 = 𝑛 𝑥=1 𝐺 (4) Theorem 4: Considering now the inverse convolution operation respect to 𝐺𝑚 ×𝑛 beside of 𝐹𝑛×1 and considering the pseudoinverse properties [18] and [21]: 𝑡𝑚 − 𝑥 𝐹 𝑥 . So that 𝐶𝑚 = 𝐺 𝑡𝑚 − 𝑥 , 𝐹 𝑥 (5) 𝐺𝑚 ×𝑛 = 𝐶𝑚×1 𝐹 ′1×𝑛 Symbolically speaking, it means that the each time interval convolution viewed as a whole respect to fixed 𝐹 𝑥 considering the inner product properties [20] and [21]: 𝐶𝑚𝑥 1 𝐺 𝑡1 − 𝑥1 𝐺 𝑡2 − 𝑥1 = ⋮ 𝐺 𝑡𝑚 − 𝑥2 𝐺 𝑡1 − 𝑥2 𝐺 𝑡2 − 𝑥2 ⋮ 𝐺 𝑡𝑚 − 𝑥2 … … ⋮ … 𝐺 𝑡1 − 𝑥𝑛 𝐺 𝑡2 − 𝑥𝑛 ⋮ 𝐺 𝑡𝑚 − 𝑥𝑛 𝑚𝑥𝑛 𝐹 𝑥1 𝐹 𝑥2 ⋮ 𝐹 𝑥𝑛 . 𝐹𝑛×1 𝐹 ′1×𝑛 + . (10) 𝑤𝑖𝑡 𝑚 ≠ 𝑛 Proof (Direct form). Respect to (1) multiplying both sides by the transpose of fix vector 𝐹𝑛×1 : (11) 𝐶𝑚×1 𝐹′1×𝑛 = 𝐺𝑚 ×𝑛 𝐹𝑛×1 𝐹′1×𝑛 (6) 𝑛𝑥 1 Representing the matrix inner product operation described in (1) ■ . And considering the singularity matrix properties, requires the pseudoinverse [18] and [21] matrix tools, obtaining (10) ■ . 3 Matrix Inverse Convolution Models Operation 4 Recursive Mean Square Error Theorem 5: The (RMSE) Recursive Mean Square Error between the trace of the original signal 𝑖 ∶= Generally in the signal processing respect to 12, 13 and 16, only observe two signals in convolution ISSN: 1790-5117 247 ISBN: 978-960-474-054-3 Proceedings of the 8th WSEAS International Conference on SIGNAL PROCESSING, ROBOTICS and AUTOMATION 𝑡𝑟𝑎𝑐𝑒 ( 𝐺𝑚 ×𝑛 ) and its estimation trace 𝑡𝑟𝑎𝑐𝑒 (𝐺𝑒𝑚 ×𝑛 ) for 𝑖 = 1, 𝑛, described as: 1 2 𝑀𝑆𝐸𝑛 = 2 𝑛 − 𝑛 + 𝑛 − 1 2 𝑀𝑆𝐸𝑛−1 𝑛 𝑖 ≔ 𝐷 𝑛 = 10 𝑙𝑜𝑔10 𝑛−1 𝐷 𝑛 − 1 = 10 𝑙𝑜𝑔10 𝑖=1 𝑛−1 (𝑖 − 𝑖 )2 + Where 10 𝑙𝑜𝑔10 (14) 𝑛−1 𝑖=1 10 𝑙𝑜𝑔10 𝑖=1 The MSE for 𝑖 = 1, 𝑛 − 1, delayed for stationary conditions 8 , [18], [19] and [21]: 1 = 𝑛−1 (15) (𝑖 − 𝑖 )2 = 𝑛 − 1 2 𝑀𝑆𝐸𝑛−1 (16) 2 𝑖2 (22) 1 𝑛−1 𝑛−1 𝑖=1 𝑖2 𝑖2 (23) 𝑖2 𝑖2 𝑖2 𝑖2 2 𝑛−1 𝑖 𝑖=1 2 − 10 𝑙𝑜𝑔10 𝑛 − 1 (24) in terms of 𝐷 𝑛 − 1 : 𝑖 = 10 𝑙𝑜𝑔10 𝑛 − 1 + 𝐷 𝑛 − 1 (25) Substituting (25) in (24): 𝑛2 𝐷 𝑛 = 10 𝑙𝑜𝑔10 2 − 10 𝑙𝑜𝑔10 2𝑛 𝑛 (26) + 10 𝑙𝑜𝑔10 𝑛 − 1 +𝐷 𝑛−1 Rewriting, using the logarithm properties, obtaining (17) ■. 𝑛−1 (𝑖 − 𝑖 )2 𝑀𝑆𝐸𝑛−1 𝑖2 And logarithms properties in it: For i = n, the last term for (13), in the same expression: 𝑛 − 𝑛 𝑖=1 𝐷 𝑛 − 1 = 10 𝑙𝑜𝑔10 𝑖=1 2 𝑛2 𝑛−1 − 20 𝑙𝑜𝑔10 𝑛 + 10 𝑙𝑜𝑔10 In the same sense of the previous concepts, with stationary properties, the decibel description for 𝑖 = 1, 𝑛 − 1: (12) Proof (Direct form). The MSE respect to the trace description for Gi , 𝑖 = 1, 𝑛, it is defined as: 𝑛 1 (13) 𝑀𝑆𝐸𝑛 = 2 (𝑖 − 𝑖 )2 𝑛 1 𝑀𝑆𝐸𝑛 = 2 𝑛 𝑛2 𝑖=1 Where respect to (15): 𝑛−1 𝑖=1 6 Bode Recursive Writing the MSE considering (16) in (14), obtaining (12) ■. Lemma 1: The Bode description as recursive expectation expressed in logarithmic scale is a function of Decibel recursive, as: (27) 𝐵 𝑛 = 0.5 𝐷(𝑛) Proof. The stochastic error considering the Bode properties and the error description in it respect to the second probability moment, for 𝑖 = 1, 𝑛, is: 5 Decibels Recursive Theorem 6: Regarding the identification defined as 𝑒𝑖 ≔ 𝑖 𝑖 . His behavior decibel recursively as: 𝑛 − 1 𝑛2 𝐷 𝑛 = 10 𝑙𝑜𝑔10 + 𝐷 𝑛 − 1 . (17) 2𝑛 𝑛2 Proof. The identification error sequence defined as an expanded vector array in mathematical expectation as: 1/2 ′ (18) 𝑒1𝑥𝑛 ≅ 𝐸 𝑒1𝑥𝑛 𝑒𝑛𝑥 1 The decibel error in stochastic way respect to second probability moment for sequence 𝑖 = 1, 𝑛 , is: ′ 𝐷 𝑛 = 20 𝑙𝑜𝑔10 𝐸 𝑒1𝑥𝑛 𝑒𝑛𝑥 1 𝑖=1,𝑛 In discrete description series: 𝑛 1 𝑖2 𝐷 𝑛 = 10 𝑙𝑜𝑔10 , 𝑛 𝑖2 1/2 1/2 ′ 𝐵 𝑛 = 10 𝑙𝑜𝑔10 𝐸 𝑒1𝑥𝑛 𝑒𝑛𝑥 1 𝑖=1,𝑛 Considering the logarithm properties: 𝑛 − 1 𝑛2 𝐵 𝑛 = 5 𝑙𝑜𝑔10 +𝐵 𝑛−1 . 2𝑛 𝑛2 The decibel corresponds to (27) ∎. The simulation illustrates the properties considered in the previous concepts, without lost the quality between two spaces; i.e., the simulation only indicates the evolution about its algorithms; depicting the convergence rate of all of its [22]. The basics distribution function considered was the Normal, with bounded variance and cero mean. In this experiment was considered a laptop Toshiba Computer (20) 𝑖=1 𝑛 −1 ISSN: 1790-5117 (29) 7 Numerical Results (19) Expanding respect to the last term: 1 𝑛2 1 𝑖2 𝐷 𝑛 = 10 𝑙𝑜𝑔10 + 𝑛 𝑛2 𝑛 2 𝑖=1 𝑖 Using the logarithms properties: (28) (21) 248 ISBN: 978-960-474-054-3 Proceedings of the 8th WSEAS International Conference on SIGNAL PROCESSING, ROBOTICS and AUTOMATION with Core Duo at 1.73 GHz, 2GB of RAM, using as software environment, the Matlab 7.0. -25 x 10 1.5 7.1 Numerical Results Theorem 2 1 MSE Fig. 1 represents in illustrative sense the function evolution 𝐹 𝑥 = 0.006 ∗ cos 𝑥 + 0.02 ∗ 𝑟𝑎𝑛𝑑𝑛 , where a pseudorandom number obtained is a 𝑟𝑎𝑛𝑑𝑛 function. 0.5 0.08 0.06 0 0 50 100 0.04 0.02 F Fig. 3 150 200 Numerical Evolution 250 300 MSE between F and its estimation Fe. 0 Fig. 4, illustrates the convergence rate between both signals (F and its estimation) [20], [21], and [22], using the decibel recursive expression (17). -0.02 -0.04 -0.06 0 50 100 150 200 Numerical Evolution 250 DR E 300 200 0 Fig.1 Original Signal F. -200 Fig 2, describes the inverse convolution operation signal Fe (the original signal estimation of F), respect to the convolution operation signal F with delayed signal G (delayed a step time), where 𝐺(𝑚, 𝑛) = 0.3 ∗ 𝑐𝑜𝑠(𝑑) + 0.02 ∗ 𝑟𝑎𝑛𝑑𝑛; so that, the new matrix expanded is a square matrix as Gm×m. -400 -600 -800 -1000 0 0.08 50 100 150 200 Numerical Evolution 250 300 0.06 Fig. 4 0.04 DRE (Decibel Recursive Error) between F and its estimation Fe. Fe 0.02 7.2 Numerical Results Theorem 3 0 -0.02 Fig. 5 represents in illustrative sense the function evolution 𝐹 𝑥 = 0.006 ∗ cos 𝑥 + 0.02 ∗ 𝑟𝑎𝑛𝑑𝑛. -0.04 -0.06 0 50 100 150 200 Numerical Evolution 250 300 Fig.2 Inverse convolution operation signal Fe. Fig. 3 shows the Mean Square Error (MSE) between F and its estimations Fe with a rate convergence round to 10-25 units. ISSN: 1790-5117 249 ISBN: 978-960-474-054-3 Proceedings of the 8th WSEAS International Conference on SIGNAL PROCESSING, ROBOTICS and AUTOMATION -20 0.08 4 0.06 3.5 x 10 3 0.04 2.5 F MSE 0.02 2 0 1.5 -0.02 1 -0.04 -0.06 0.5 0 Fig.5 50 100 150 200 Numerical Evolution 250 0 300 Original Signal F. 0 Fig. 7 Fig 6, describes the inverse convolution operation obtained as signal Fe (the original signal estimation of F), respect to have the convolutioned signal F with delayed signal G (delayed a step time), where 𝐺(𝑚, 𝑛) = 0.3 ∗ 𝑐𝑜𝑠(𝑑) + 0.02 ∗ 𝑟𝑎𝑛𝑑𝑛 ; so that, the new matrix expanded generated is not square matrix Gm×n. 50 100 150 200 Numerical Evolution 250 300 MSE between F and its estimation Fe. Fig. 8, illustrates the convergence rate between both signals (F and its estimation), using the decibel recursive expression (17). DRE 200 0 0.08 -200 0.06 -400 0.04 -600 Fe 0.02 -800 0 -1000 0 -0.02 50 100 150 200 Numerical Evolution 250 300 -0.04 -0.06 Fig. 8 0 50 100 150 200 Numerical Evolution 250 300 7.3 Numerical Results Theorem 4 Fig.6 Inverse convolution operation signal Fe. Fig. 9 represents in illustrative sense the function evolution 𝐺(𝑚, 𝑛) = 0.3 ∗ 𝑐𝑜𝑠(𝑑) + 0.02 ∗ 𝑟𝑎𝑛𝑑𝑛 , where 𝑟𝑎𝑛𝑑𝑛 is a pseudorandom Matlab number. Fig. 7 shows the MSE between F and its estimation Fe has a rate convergence round to 10-25 units. ISSN: 1790-5117 DRE (Decibel Recursive Error) between F and its estimation Fe. 250 ISBN: 978-960-474-054-3 Proceedings of the 8th WSEAS International Conference on SIGNAL PROCESSING, ROBOTICS and AUTOMATION 0.4 0.09 0.3 0.08 0.07 0.2 0.06 MSE G 0.1 0 0.05 0.04 -0.1 0.03 -0.2 0.02 -0.3 -0.4 0.01 0 50 100 150 200 Numerical Evolution 250 0 300 0 50 100 150 200 Numerical Evolution 250 300 Fig.9 Original Signal F. Fig. 11 Fig. 10, describes the inverse convolution operation signal Ge (signal estimation of G), respect to the convolution operation signal F with delayed signal G (delayed a step time), where 𝐹 𝑥 = 0.006 ∗ cos 𝑥 + 0.02 ∗ 𝑟𝑎𝑛𝑑𝑛. Fig. 1, illustrates the convergence rate between both signals (F and its estimation), using the decibel recursive expression (17). DRE MSE between F and its estimation Fe. 4000 3500 0.08 3000 0.06 2500 0.04 2000 Ge 0.02 1500 0 1000 -0.02 500 -0.04 0 -0.06 -0.08 0 50 100 150 200 Numerical Evolution 250 0 Inverse convolution operation signal Fe. 60 80 100 120 140 Numerical Evolution 160 180 200 DRE (Decibel Recursive Error) between F and its estimation Fe. The first simulation model respect to inverse convolution operation (7) showed a rate convergence round to 10-25 (Fig. 3). The second model of inverse convolution operation (8) showed a rate convergence round to 10-20 (Fig. 7). Finally the third model (10) showed a rate convergence round to 10-4 (Fig. 11). Moreover the first and the second model in its decibel diagram illustrated the convergence rate between both signals: F and its estimation (Fig. 4 and Fig. 8, respectively). But in the case of the third model illustrated in decibel form didn`t convergence between both signals: G and its estimation (Fig. 12). Fig. 11 shows the MSE between G and its estimation Ge with a rate convergence round to 10-25 Matlab units. ISSN: 1790-5117 40 300 Fig. 12 Fig.10 20 251 ISBN: 978-960-474-054-3 Proceedings of the 8th WSEAS International Conference on SIGNAL PROCESSING, ROBOTICS and AUTOMATION 8 Conclusions This paper gave a short introduction and description defining the inverse convolution operation in basic structure and explains with short comments some of its applications in astronomy, microscopy and analysis of seismic measures, in the others. The second part presented formal convolution and inverse convolution operation concepts about various issues concerned. The first corresponded to convolution as a matrix expands expression, which provided the necessary preamble to define the three models respect to inverse convolution operation matrix suggested in this work. Requiring in probability manner the mean square error, observing its convergence rate trough diagrams Decibels description according to the proposed Inverse convolution operation models in simulation graphs. Showing this section observing the three inverse convolution operation methods in simulation scheme where the third was the best in convergence rate. Graphically speaking compared the inverse convolution operation signals respect to original signal in trace operation sense. The convergence error functional was obtained respect to mean square error in vector description, using the second probability moment and Decibels expression in recursive form. So that, analyzing the results could be concluded that the novel optimal inverse convolution operation was the good enough estimation methods. [3] K. Ogata., Discrete Time Control Systems, Prentice Hall, 1996. E. Solar., L. Speziale., Linear Algebra Notes, Limusa, 1999. S. I. Grossman., Algebra Lineal, McGraw-Hill, 1996. B. Noble, J.W. Daniel, Applied Linear Algebra, Prentice Hall, 1989. [5] [6] [7] D.C. Lay., Linear Algebra and its Applications, Pearson, 1999. [8] V.S. Pugachev., Introduction to the Theory of Probability, Mir Moscu, 1973. [9] W. Mendenhall., T. Sincich., Probability and Statistics for Engineering and Science, Prentice Hall, 1997. [10] Walpole., Myers., Probability and Statistics, McGraw-Hill, 1999. [11] M.J. Marques., Probability and Statistics for Chemical Biological Sciences, UNAM, 1988. [12] W.H. Hayt., J.E. Kemmerly., Analysis Circuit in Engineerin, McGraw-Hill, 1993. [13] A. Papoulis, M. Bertran., Digital and Analog Systems and Circuits, Marcombo, 1989. The first simulation model respect to inverse convolution operation (7) showed a rate convergence round to 10-25 (Fig. 3). The second model of inverse convolution operation (8) showed a rate convergence round to 10-20 (Fig. 7). Finally the third model (10) showed a rate convergence round to 10-4 (Fig. 11). Moreover the first and the second model in its decibel diagram illustrated the convergence rate between both signals: F and its estimation (Fig. 4 and Fig. 8, respectively). But in the case of the third model illustrated in decibel form didn`t convergence between both signals: G and its estimation (Fig. 12). [14] R.L. Boylestad., Introductory Analysis Circuit, Pretince Hall, 1997. [15] D.C. Baird., Experimentation, An Introduction to the Theory of Measurement and Design of Experiments, Pearson, 1991. [16] M.S. Grewal., A.P. Andrews., Kalman Filtering Theory and Practice, Prentice Hall, 1993. References: [17] M.A. Toledo., J.J. Medel., Priority tasks allocation through the maximum entropy principle, Proceedings of the 8th Conference on 8th WSEAS International Conference on Automation and Information, Vol. 8, 2007, pp. 271-276. [18] A.S. Poznyak., K. Najim., Learning Automata J. I. De la Rosa et.al, A Comparative Evaluation of four Algorithms for Numeric Solution of the Deconvolution on Unidimensional Systems, Computación y Sistemas, Vol. 10, No. 2, 2006, pp. 135-158. ISSN: 1790-5117 S. Cordero, Seismograms Deconvolution by Digital Division and Inverse Filtering Spectral Simulation and Digital Seismograms, Compendium of Research Papers. CNDG Library Geophysical Institute of Peru, Vol. 4, 2003, pp.131-146. [4] The matrix inverse convolution operation model, in discrete form, recovered the signal through the inverse matrices and pseudoinverse schemes. [1] [2] 252 ISBN: 978-960-474-054-3 Proceedings of the 8th WSEAS International Conference on SIGNAL PROCESSING, ROBOTICS and AUTOMATION and Stochastic Optimization, Springer-Verlag, 1997. [19] F.J. Bejarano.,A. Poznyak., Hierarchical second-order sliding-mode observer for linear time invariant systems with unknown inputs, International Journal of Systems Science, Vol. 38, 2007, pp. 793-802. [20] J.C. García., J.J. Medel., P. Guevara, RTFDF description for ARMA systems, Proceedings of the 8th Conference on 8th WSEAS International Conference on Fuzzy Systems, Vol. 8, 2007, pp.192-195. [21] J.J. Medel., P. Guevara., D. Cruz, Matricial estimation for start times with stochastic behaivor by periodic real time tasks in a concurrent system, Proceedings of the 7th WSEAS International Conference on Mathematical Methods and Computational Techniques In Electrical Engineering, 2005, pp. 214-217. [22] J. Clempner., J. Medel., A Lyapunov., Shortest-path characterization for Markov decision processes, Mathematics And Computers In Science And Engineering Proceedings of the American Conference on Applied Mathematics,2008, pp. 143-147. ISSN: 1790-5117 253 ISBN: 978-960-474-054-3
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