Reports de recercahttp://hdl.handle.net/2117/39192024-03-28T10:38:03Z2024-03-28T10:38:03ZSoftware prototype for the Galileo ionospheric correction model: progress reportAragón Ángel, María ÁngelesZürn, M.http://hdl.handle.net/2117/3969042023-11-22T13:00:19Z2023-11-22T12:50:54ZSoftware prototype for the Galileo ionospheric correction model: progress report
Aragón Ángel, María Ángeles; Zürn, M.
The document describing the particular ionospheric model developed for the Galileo satellite navigation system has been officially released [1]. Its publication allows GNSS receiver manufacturers to start the implementation of the specific algorithm targeted for their Galileo related products in order to be compliant with the Galileo system. Some of such implementations have already been supported by Unit G05 (now E.2) in the framework of an on-going support activity under the EU GNSS Programmes with DG GROW and GSA, responding to inquiries from the receiver manufacturers Broadcom and Javad. The only way to support the development of the new Galileo ionospheric correction in an efficient and timely manner is to have our own developed model as an official Galileo Programme reference (i.e. the European Commission) product to assess and help correcting external implementations, which will definitely have a direct impact on industry and, in return, society. Once the JRC NeQuickG product is available, further developments have been already foreseen: optimize the algorithm and tailor it to the needs of the various users, notably in terms of accuracy.
This particular report includes a description of the JRC NeQuick source code (JRC NeQuickG) and comments on the challenges faced to implement it. Emphasis on the System Architecture is put in order to help any potential follow up of this project in the near future.
This particular report includes a description of the JRC NeQuick source code (JRC NeQuickG) and comments on the challenges faced to implement it. Emphasis on the System Architecture is put in order to help any potential follow up of this project in the near future.
2023-11-22T12:50:54ZAragón Ángel, María ÁngelesZürn, M.The document describing the particular ionospheric model developed for the Galileo satellite navigation system has been officially released [1]. Its publication allows GNSS receiver manufacturers to start the implementation of the specific algorithm targeted for their Galileo related products in order to be compliant with the Galileo system. Some of such implementations have already been supported by Unit G05 (now E.2) in the framework of an on-going support activity under the EU GNSS Programmes with DG GROW and GSA, responding to inquiries from the receiver manufacturers Broadcom and Javad. The only way to support the development of the new Galileo ionospheric correction in an efficient and timely manner is to have our own developed model as an official Galileo Programme reference (i.e. the European Commission) product to assess and help correcting external implementations, which will definitely have a direct impact on industry and, in return, society. Once the JRC NeQuickG product is available, further developments have been already foreseen: optimize the algorithm and tailor it to the needs of the various users, notably in terms of accuracy.
This particular report includes a description of the JRC NeQuick source code (JRC NeQuickG) and comments on the challenges faced to implement it. Emphasis on the System Architecture is put in order to help any potential follow up of this project in the near future.Beacon Satellite Symposium: Session 5B - June 30th 2016: Radio occultation techniques and measurementsAragón Ángel, María Ángeleshttp://hdl.handle.net/2117/3969002023-11-22T12:20:13Z2023-11-22T12:17:18ZBeacon Satellite Symposium: Session 5B - June 30th 2016: Radio occultation techniques and measurements
Aragón Ángel, María Ángeles
During the Beacon Satellite Symposium, held in Trieste, Italy, between June 26 and July 1 2016, the JRC chaired the session 5B: Radio Occultation Techniques and Measurements. The corresponding abstract of the session is provided as follows: Since the mid-1960s, the GNSS based radio occultation technique has been used to study the structure and properties of the atmospheres of not only Earth but also other planets, such as Venus, Mars, some other outer planets, and many of their moons. By measuring the phase delay of radio waves from GNSS satellites as they are occulted by the Earth’s atmosphere, the vertical density profiles of the bending angles of radio wave trajectories can be estimated using measurements onboard LEO satellites. The success of the GPS/MET mission in 1995 inspired a number of follow-on missions that include radio occultation experiment, including the CHAMP, GRACE, SAC-C, COSMIC, Metop-A/B, C/NOFS, and upcoming COSMIC-2 satellites. The combined profiles from these different LEO satellites provide excellent opportunities to explore the dynamics and structure of the ionosphere, especially in the regions that have been devoid of ground-based instruments, allowing for investigation of the longitudinal variability of the ionospheric density structure. This session seeks contributions that advance the application of RO technique for space weather studies. In addition, we welcome presentations exploring innovative methodologies that address the current problem on RO inversion technique at the equatorial region where ionospheric irregularity, such as sporadic E and spread F, present and degrade the linear combination technique that affect the quality of density profile extracted in the region. The session was organized among Endawoke Yizengaw (Institute for Scientific Research, Boston College), Jann-Yenq Liu (National Space Organization –NSPO- Chief Scientist), and Angela Aragon-Angel (Joint Research Centre). The session consisted of both oral and poster presentation parts.
2023-11-22T12:17:18ZAragón Ángel, María ÁngelesDuring the Beacon Satellite Symposium, held in Trieste, Italy, between June 26 and July 1 2016, the JRC chaired the session 5B: Radio Occultation Techniques and Measurements. The corresponding abstract of the session is provided as follows: Since the mid-1960s, the GNSS based radio occultation technique has been used to study the structure and properties of the atmospheres of not only Earth but also other planets, such as Venus, Mars, some other outer planets, and many of their moons. By measuring the phase delay of radio waves from GNSS satellites as they are occulted by the Earth’s atmosphere, the vertical density profiles of the bending angles of radio wave trajectories can be estimated using measurements onboard LEO satellites. The success of the GPS/MET mission in 1995 inspired a number of follow-on missions that include radio occultation experiment, including the CHAMP, GRACE, SAC-C, COSMIC, Metop-A/B, C/NOFS, and upcoming COSMIC-2 satellites. The combined profiles from these different LEO satellites provide excellent opportunities to explore the dynamics and structure of the ionosphere, especially in the regions that have been devoid of ground-based instruments, allowing for investigation of the longitudinal variability of the ionospheric density structure. This session seeks contributions that advance the application of RO technique for space weather studies. In addition, we welcome presentations exploring innovative methodologies that address the current problem on RO inversion technique at the equatorial region where ionospheric irregularity, such as sporadic E and spread F, present and degrade the linear combination technique that affect the quality of density profile extracted in the region. The session was organized among Endawoke Yizengaw (Institute for Scientific Research, Boston College), Jann-Yenq Liu (National Space Organization –NSPO- Chief Scientist), and Angela Aragon-Angel (Joint Research Centre). The session consisted of both oral and poster presentation parts.Stallings automata and applications : BGSMath graduate courseDelgado Rodríguez, JordiVentura Capell, EnricWeil, Pascalhttp://hdl.handle.net/2117/3951132023-10-19T11:20:21Z2023-10-19T11:17:45ZStallings automata and applications : BGSMath graduate course
Delgado Rodríguez, Jordi; Ventura Capell, Enric; Weil, Pascal
The theory of Stallings automata provides a neat geometric representation of subgroups of the free group, and constitutes the modern —and probably the most natural and fruitful — approach to their study. Moreover, if the involved subgroups are finitely generated, then this description is finitary and very well suited for algorithmic treatment. The original result (hinted by the work of Serre, and stated in a seminal paper bytallings in 1983) interprets the subgroups of a free group FA as covering spaces of the bouquet of n circles. This mainly topological original viewpoint, has been converted into a more combinatorial one during the last decades, with the use of automata; this stresses the fact that, when restricted to finitely generated subgroups, most of the interesting problems can be resolved in a computational way, with algorithms usually more efficient and easy to understand than classical ones (more algebraic oriented). The goal of this Advanced Graduate Course is to introduce the student into the world of free groups, to show him/her the intrinsic complexity of this algebraic structure and of the natural problems emanating from it, and to introduce him/her into the modern Stallings techniques, able to solve most of the classical problems and many new ones in a quite comprehensible and graphical way (and not using much technicalities). We’ll continuously emphasise the computational point of view, not just giving formal mathematical proofs, but also providing algorithms able to do the tasks effectively by using present time computers. On one hand, this is a research topic relatively easy to get in, since the background needed is just some basic knowledge of algebra and graph theory. On the other hand, it is a hot research topic with lots of papers published since Stallings seminal paper in 1983 using these techniques, and lots that continue appearing in our days. A significant part of the publications of the three proposed lecturers use Stallings graphical techniques in an essential way. See the two recent surveys [2] and [4] from the bibliography below. The course will cover full proofs of several classical results about subgroups of free groups, like Nielsen-Schreier Theorem, Schreier index formula, Marshall Hall Theorem, membership problem, residual finiteness, the Howson property, Hanna-Neumann inequality, etc. But we plan to also introduce more advanced material in direct connection with research done in the last years: techniques for counting Stallings graphs and so for giving asymptotic estimates about properties of subgroups of the free group, enriched Stallings graphs allowing to extend results to certain groups of the form Fn X Zm or, more generally, Fn X A Zm, etc. Some connections with the theory of right-angled Artin groups will also be explained.
The goal of this Advanced Graduate Course is to introduce the student into the world of free groups, to show the intrinsic complexity of this algebraic structure and of the natural problems emanating from it, and to introduce the modern Stallings techniques, able to solve most of the classical problems and many new ones in a quite comprehensible and graphical way. We’ll emphasize the computational point of view, not just giving formal proofs, but also providing algorithms able to do the tasks effectively.
The course will cover several classical results, like Nielsen-Schreier Theorem, Schreier index formula, Marshall Hall Theorem, membership problem, residual finiteness, the Howson property, Hanna-Neumann inequality, etc. But we plan to also introduce more advanced material in direct connection with research done in the last years: techniques for giving asymptotic estimates of properties of subgroups of the free group, enriched Stallings graphs allowing to extend results to broader families.
2023-10-19T11:17:45ZDelgado Rodríguez, JordiVentura Capell, EnricWeil, PascalThe theory of Stallings automata provides a neat geometric representation of subgroups of the free group, and constitutes the modern —and probably the most natural and fruitful — approach to their study. Moreover, if the involved subgroups are finitely generated, then this description is finitary and very well suited for algorithmic treatment. The original result (hinted by the work of Serre, and stated in a seminal paper bytallings in 1983) interprets the subgroups of a free group FA as covering spaces of the bouquet of n circles. This mainly topological original viewpoint, has been converted into a more combinatorial one during the last decades, with the use of automata; this stresses the fact that, when restricted to finitely generated subgroups, most of the interesting problems can be resolved in a computational way, with algorithms usually more efficient and easy to understand than classical ones (more algebraic oriented). The goal of this Advanced Graduate Course is to introduce the student into the world of free groups, to show him/her the intrinsic complexity of this algebraic structure and of the natural problems emanating from it, and to introduce him/her into the modern Stallings techniques, able to solve most of the classical problems and many new ones in a quite comprehensible and graphical way (and not using much technicalities). We’ll continuously emphasise the computational point of view, not just giving formal mathematical proofs, but also providing algorithms able to do the tasks effectively by using present time computers. On one hand, this is a research topic relatively easy to get in, since the background needed is just some basic knowledge of algebra and graph theory. On the other hand, it is a hot research topic with lots of papers published since Stallings seminal paper in 1983 using these techniques, and lots that continue appearing in our days. A significant part of the publications of the three proposed lecturers use Stallings graphical techniques in an essential way. See the two recent surveys [2] and [4] from the bibliography below. The course will cover full proofs of several classical results about subgroups of free groups, like Nielsen-Schreier Theorem, Schreier index formula, Marshall Hall Theorem, membership problem, residual finiteness, the Howson property, Hanna-Neumann inequality, etc. But we plan to also introduce more advanced material in direct connection with research done in the last years: techniques for counting Stallings graphs and so for giving asymptotic estimates about properties of subgroups of the free group, enriched Stallings graphs allowing to extend results to certain groups of the form Fn X Zm or, more generally, Fn X A Zm, etc. Some connections with the theory of right-angled Artin groups will also be explained.State-of-art products for real time scintillation monitoring and consolidated requirements for the activityGonzález Casado, GuillermoJuan Zornoza, José MiguelYin, YuTimote Bejarano, Cristhian CamiloSanz Subirana, JaumeRovira Garcia, Adriàhttp://hdl.handle.net/2117/3919012023-10-22T00:04:09Z2023-07-21T07:49:32ZState-of-art products for real time scintillation monitoring and consolidated requirements for the activity
González Casado, Guillermo; Juan Zornoza, José Miguel; Yin, Yu; Timote Bejarano, Cristhian Camilo; Sanz Subirana, Jaume; Rovira Garcia, Adrià
The first phase of the RT-WMIS activity comprises two Work Packages (WPs). WP 10 is aimed at performing a revision of the state-of-the-art RT products and requirements for the RT-WMIS activity. On the other hand, WP 20 is devoted to carry out the software design for the subsequent implementation of the RT-WMIS tool. The present technical note (TN-1) describes the activities developed in the framework of WP 10.
2023-07-21T07:49:32ZGonzález Casado, GuillermoJuan Zornoza, José MiguelYin, YuTimote Bejarano, Cristhian CamiloSanz Subirana, JaumeRovira Garcia, AdriàOn some rational piecewise linear rotationsCima, AnnaGasull, ArmengolMañosa Fernández, VíctorMañosas, Franceschttp://hdl.handle.net/2117/3909222023-07-14T11:30:29Z2023-07-14T11:27:01ZOn some rational piecewise linear rotations
Cima, Anna; Gasull, Armengol; Mañosa Fernández, Víctor; Mañosas, Francesc
We study the dynamics of the piecewise planar rotations $F_{\lambda}(z)=\lambda (z-H(z)),
$ with $z\in\C$, $H(z)=1$ if $\mathrm{Im}(z)\ge0,$ $H(z)=-1$ if $\mathrm{Im}(z)<0,$ and $\lambda=\mathrm{e}^{i \alpha} \in\C$, being $\alpha$ a rational multiple of $\pi$. Our main results establish the dynamics in the so called regular set, which is the complementary of the closure of the set formed by the preimages of the discontinuity line. We prove that any connected component of this set is open, bounded and periodic under the action of $F_\lambda$, with a period $\ell,$ that depends on the connected component. Furthermore, $F_\lambda^\ell $ restricted to each component acts as a rotation with a period which also depends on the connected component. As a consequence, any point in the regular set is periodic. Among other results, we also prove that for any connected component of the regular set, its boundary
is a convex polygon with certain maximum number of sides.
2023-07-14T11:27:01ZCima, AnnaGasull, ArmengolMañosa Fernández, VíctorMañosas, FrancescWe study the dynamics of the piecewise planar rotations $F_{\lambda}(z)=\lambda (z-H(z)),
$ with $z\in\C$, $H(z)=1$ if $\mathrm{Im}(z)\ge0,$ $H(z)=-1$ if $\mathrm{Im}(z)<0,$ and $\lambda=\mathrm{e}^{i \alpha} \in\C$, being $\alpha$ a rational multiple of $\pi$. Our main results establish the dynamics in the so called regular set, which is the complementary of the closure of the set formed by the preimages of the discontinuity line. We prove that any connected component of this set is open, bounded and periodic under the action of $F_\lambda$, with a period $\ell,$ that depends on the connected component. Furthermore, $F_\lambda^\ell $ restricted to each component acts as a rotation with a period which also depends on the connected component. As a consequence, any point in the regular set is periodic. Among other results, we also prove that for any connected component of the regular set, its boundary
is a convex polygon with certain maximum number of sides.On the accumulation points of non-periodic orbits of a difference equation of fourth orderLinero Bas, AntonioMañosa Fernández, VíctorNieves Roldán, Danielhttp://hdl.handle.net/2117/3909192023-07-14T11:20:14Z2023-07-14T11:15:26ZOn the accumulation points of non-periodic orbits of a difference equation of fourth order
Linero Bas, Antonio; Mañosa Fernández, Víctor; Nieves Roldán, Daniel
In this paper, we are interested in analyzing the dynamics of the fourth-order difference equation x_{n+4}=max{x_{n+3},x_{n+2},x_{n+1},0}-x_n, with arbitrary real initial conditions. We fully determine the accumulation point sets of the non-periodic solutions that, in fact, are configured as proper compact intervals of the real line. This study complements the previous knowledge of the dynamics of the difference equation already achieved in [M. Csörnyei, M. Laczkovich, Monatsh. Math. 132 (2001), 215-236] and [A. Linero Bas, D. Nieves Roldán, J. Difference Equ. Appl. 27 (2021), no. 11, 1608-1645]
Preprint
2023-07-14T11:15:26ZLinero Bas, AntonioMañosa Fernández, VíctorNieves Roldán, DanielIn this paper, we are interested in analyzing the dynamics of the fourth-order difference equation x_{n+4}=max{x_{n+3},x_{n+2},x_{n+1},0}-x_n, with arbitrary real initial conditions. We fully determine the accumulation point sets of the non-periodic solutions that, in fact, are configured as proper compact intervals of the real line. This study complements the previous knowledge of the dynamics of the difference equation already achieved in [M. Csörnyei, M. Laczkovich, Monatsh. Math. 132 (2001), 215-236] and [A. Linero Bas, D. Nieves Roldán, J. Difference Equ. Appl. 27 (2021), no. 11, 1608-1645]Counting configurations of limit cycles and centersGasull, ArmengolGuillamon Grabolosa, AntoniMañosa Fernández, Víctorhttp://hdl.handle.net/2117/3909172023-07-14T11:10:16Z2023-07-14T11:01:29ZCounting configurations of limit cycles and centers
Gasull, Armengol; Guillamon Grabolosa, Antoni; Mañosa Fernández, Víctor
We present several results on the determination of the number and distribution of limit cycles or centers for planar systems of differential equations. In most cases, the study of a recurrence is one of the key points of our approach. These results include the counting of the number of configurations of stabilities of nested limit cycles, the study of the number of different configurations of a given number of limit cycles, the proof of some quadratic lower bounds for Hilbert numbers and some questions about the number of centers for planar polynomial vector fields.
2023-07-14T11:01:29ZGasull, ArmengolGuillamon Grabolosa, AntoniMañosa Fernández, VíctorWe present several results on the determination of the number and distribution of limit cycles or centers for planar systems of differential equations. In most cases, the study of a recurrence is one of the key points of our approach. These results include the counting of the number of configurations of stabilities of nested limit cycles, the study of the number of different configurations of a given number of limit cycles, the proof of some quadratic lower bounds for Hilbert numbers and some questions about the number of centers for planar polynomial vector fields.Splitting of separatrices for rapid degenerate perturbations of the classical pendulumBaldomá Barraca, InmaculadaMartínez-Seara Alonso, M. TeresaMoreno González, Románhttp://hdl.handle.net/2117/3874792023-05-16T10:40:17Z2023-05-16T10:39:09ZSplitting of separatrices for rapid degenerate perturbations of the classical pendulum
Baldomá Barraca, Inmaculada; Martínez-Seara Alonso, M. Teresa; Moreno González, Román
In this work we study the splitting distance of a rapidly perturbed pendulum H(x, y, t) = 1 2 y 2 + (cos(x) - 1) + µ(cos(x) - 1)g t e with g(t ) = P |k|>1 g [k] e ikt a 2p-periodic function and µ, e 1. Systems of this kind undergo exponentially small splitting and, when µ 1, it is known that the Melnikov function actually gives an asymptotic expression for the splitting function provided g [±1] 6= 0. Our study focuses on the case g [±1] = 0 and it is motivated by two main reasons. On the one hand the general understanding of the splitting, as current results fail for a perturbation as simple as g(t ) = cos(5t ) + cos(4t ) + cos(3t ). On the other hand, a study of the splitting of invariant manifolds of tori of rational frequency p/q in Arnold’s original model for diffusion leads to the consideration of pendulum-like Hamiltonians with g(t ) = sin p · t e + cos q · t e , where, for most p, q ¿ Z the perturbation satisfies g [±1] 6= 0. As expected, the Melnikov function is not a correct approximation for the splitting in this case. To tackle the problem we use a splitting formula based on the solutions of the so-called inner equation and make use of the Hamilton-Jacobi formalism. The leading exponentially small term appears at order µ n , where n is an integer determined exclusively by the harmonics of the perturbation. We also provide an algorithm to compute it.
2023-05-16T10:39:09ZBaldomá Barraca, InmaculadaMartínez-Seara Alonso, M. TeresaMoreno González, RománIn this work we study the splitting distance of a rapidly perturbed pendulum H(x, y, t) = 1 2 y 2 + (cos(x) - 1) + µ(cos(x) - 1)g t e with g(t ) = P |k|>1 g [k] e ikt a 2p-periodic function and µ, e 1. Systems of this kind undergo exponentially small splitting and, when µ 1, it is known that the Melnikov function actually gives an asymptotic expression for the splitting function provided g [±1] 6= 0. Our study focuses on the case g [±1] = 0 and it is motivated by two main reasons. On the one hand the general understanding of the splitting, as current results fail for a perturbation as simple as g(t ) = cos(5t ) + cos(4t ) + cos(3t ). On the other hand, a study of the splitting of invariant manifolds of tori of rational frequency p/q in Arnold’s original model for diffusion leads to the consideration of pendulum-like Hamiltonians with g(t ) = sin p · t e + cos q · t e , where, for most p, q ¿ Z the perturbation satisfies g [±1] 6= 0. As expected, the Melnikov function is not a correct approximation for the splitting in this case. To tackle the problem we use a splitting formula based on the solutions of the so-called inner equation and make use of the Hamilton-Jacobi formalism. The leading exponentially small term appears at order µ n , where n is an integer determined exclusively by the harmonics of the perturbation. We also provide an algorithm to compute it.The Arnold conjecture for singular symplectic manifoldsBrugués Mora, JoaquinMiranda Galcerán, EvaOms, Cedrichttp://hdl.handle.net/2117/3862552023-04-23T02:20:52Z2023-04-14T13:34:47ZThe Arnold conjecture for singular symplectic manifolds
Brugués Mora, Joaquin; Miranda Galcerán, Eva; Oms, Cedric
In this article, we study the Hamiltonian dynamics on singular symplectic manifolds and prove the Arnold conjecture for a large class of bm-symplectic manifolds. More precisely, we prove a lower bound on the number 1-periodic Hamiltonian orbits for b2m-symplectic manifolds depending only on the topology of the manifold. Moreover, for bm-symplectic surfaces, we improve the lower bound depending on the topology of the pair (M, Z). We then venture into the study of Floer homology to this singular realm and we conclude with a list of open questions.
2023-04-14T13:34:47ZBrugués Mora, JoaquinMiranda Galcerán, EvaOms, CedricIn this article, we study the Hamiltonian dynamics on singular symplectic manifolds and prove the Arnold conjecture for a large class of bm-symplectic manifolds. More precisely, we prove a lower bound on the number 1-periodic Hamiltonian orbits for b2m-symplectic manifolds depending only on the topology of the manifold. Moreover, for bm-symplectic surfaces, we improve the lower bound depending on the topology of the pair (M, Z). We then venture into the study of Floer homology to this singular realm and we conclude with a list of open questions.How to avoid repetitions in lattice-based deniable zero-knowledge proofsArnal i Clemente, XavierCano Aguilera, AbrahamFinogina, TamaraHerranz Sotoca, Javierhttp://hdl.handle.net/2117/3769892023-10-29T10:01:41Z2022-11-23T11:58:09ZHow to avoid repetitions in lattice-based deniable zero-knowledge proofs
Arnal i Clemente, Xavier; Cano Aguilera, Abraham; Finogina, Tamara; Herranz Sotoca, Javier
Interactive zero-knowledge systems are a very important cryptographic primitive, used in many applications, especially when deniability (also known as non-transferability) is desired. In the lattice-based setting, the currently most efficient interactive zero-knowledge systems employ the technique of rejection sampling, which implies that the interaction does not always finish correctly in the first execution; the whole interaction must be re-run until abort does not happen. While repetitions due to aborts are acceptable in theory, in some practical applications it is desirable to avoid re-runs for usability reasons. In this work we present a generic technique that departs from an interactive zero-knowledge system (that might require multiple re-runs to complete the protocol) and obtains a 3-moves zero-knowledge system (without re-runs). The transformation combines the well-known Fiat-Shamir technique with a couple of initially exchanged messages. The resulting 3-moves system enjoys honest-verifier zero-knowledge and can be easily turned into a fully deniable proof using standard techniques. We show some practical scenarios where our transformation can be beneficial and we also discuss the results of an implementation of our transformation.
2022-11-23T11:58:09ZArnal i Clemente, XavierCano Aguilera, AbrahamFinogina, TamaraHerranz Sotoca, JavierInteractive zero-knowledge systems are a very important cryptographic primitive, used in many applications, especially when deniability (also known as non-transferability) is desired. In the lattice-based setting, the currently most efficient interactive zero-knowledge systems employ the technique of rejection sampling, which implies that the interaction does not always finish correctly in the first execution; the whole interaction must be re-run until abort does not happen. While repetitions due to aborts are acceptable in theory, in some practical applications it is desirable to avoid re-runs for usability reasons. In this work we present a generic technique that departs from an interactive zero-knowledge system (that might require multiple re-runs to complete the protocol) and obtains a 3-moves zero-knowledge system (without re-runs). The transformation combines the well-known Fiat-Shamir technique with a couple of initially exchanged messages. The resulting 3-moves system enjoys honest-verifier zero-knowledge and can be easily turned into a fully deniable proof using standard techniques. We show some practical scenarios where our transformation can be beneficial and we also discuss the results of an implementation of our transformation.