arXiv subjects

M. Munoz

Publications and source records attributed to M. Munoz.

10 recordsLinked to original sources

arXiv2026

Robodimm: A Physics-Grounded Framework for Automated Actuator Sizing in Scalable Modular Robots

Selecting an appropriate motor-gearbox combination is a critical design task in robotics because it directly affects cost, mass, and dynamic performance. This process is especially challenging in modular robots with closed kinematic chains, where joint torques are coupled and actuator inertia propagates through the mechanism. We present Robodimm, a software framework for automated actuator sizing in scalable robot architectures. By leveraging Pinocchio for dynamics and Pink for inverse kinematics, Robodimm uses a Karush-Kuhn-Tucker (KKT) formulation for constrained inverse dynamics. The platform supports parametric scaling, interactive trajectory programming through jog modes, and a two-round validation workflow that addresses actuator self-weight effects.

cs.RO↗

arXiv2018

The Shortest-period Wolf-Rayet binary in the Small Magellanic Cloud: Part of a high-order multiple system

SMC AB 6 is the shortest-period (6.5d) Wolf-Rayet (WR) binary in the Small Magellanic Cloud, and is therefore crucial for the study of binary interaction and formation of WR stars at low metallicity. The WR component in AB 6 was previously found to be very luminous (logL=6.3[Lsun]) compared to its reported orbital mass (8Msun), placing it significantly above the Eddington limit. Through spectroscopy and orbital analysis of newly acquired optical data taken with UVES, we aim to understand the peculiar results reported for this system and explore its evolutionary history. Results: We find that AB 6 contains at least four stars. The 6.5d period WR binary comprises the WR primary (WN3:h, star A) and a rather rapidly rotating early O-type companion (O5.5 V, star B). Static N and He lines suggest the presence of an emission line star (O5.5 I(f), star C). Finally, narrow absorption lines portraying a long-term radial velocity variation show the existence of a fourth star (O7.5 V, star D). Star D appears to form a second 140d period binary together with a fifth stellar member, which is a B-type dwarf or a black hole. It is not clear that these additional components are bound to the WR binary. The WR star is found to be less luminous than previously thought (logL = 5.9[Lsun]) and, adopting 41Msun for star B, more massive (18Msun). Correspondingly, the WR star does not exceed the Eddington limit. We derive the initial masses of 60 and 40Msun for stars A and B and an age of 3.9 Myr for the system. The WR binary likely experienced nonconservative mass transfer in the past supported by the relatively rapid rotation of star B. Conclusion: Our study shows that AB 6 is a multiple -- probably quintuple -- system. This finding resolves the previously reported puzzle of the WR primary exceeding the Eddington limit and suggests that the WR star exchanged mass with its companion in the past.

astro-ph.SR↗

arXiv2018

The NIKA2 instrument at 30-m IRAM telescope: performance and results

The New IRAM KID Arrays 2 (NIKA2) consortium has just finished installing and commissioning a millimetre camera on the IRAM 30 m telescope. It is a dual-band camera operating with three frequency multiplexed kilo-pixels arrays of Lumped Element Kinetic Inductance Detectors (LEKID) cooled at 150 mK, designed to observe the intensity and polarisation of the sky at 260 and 150 GHz (1.15 and 2 mm). NIKA2 is today an IRAM resident instrument for millimetre astronomy, such as Intra Cluster Medium from intermediate to distant clusters and so for the follow-up of Planck satellite detected clusters, high redshift sources and quasars, early stages of star formation and nearby galaxies emission. We present an overview of the instrument performance as it has been evaluated at the end of the commissioning phase.

astro-ph.IM↗

arXiv2015

Efficient Synchronization of Dipolarly Coupled Vortex-Based Spin Transfer Nano-Oscillators

Due to their nonlinear properties, spin transfer nano-oscillators can easily adapt their frequency to external stimuli. This makes them interesting model systems to study the effects of synchronization and brings some opportunities to improve their microwave characteristics in view of their applications in information and communication technologies and to design innovative computing architectures. So far, mutual synchronization of spin transfer nano-oscillators through propagating spin-waves and exchange coupling in a common magnetic layer has been demonstrated. Here we show that the dipolar interaction is also an efficient mechanism to synchronize neighbouring oscillators. We experimentally study a pair of vortex-based spin-transfer nano-oscillators, in which mutual synchronization can be achieved despite a significant frequency mismatch between oscillators. Importantly, the coupling efficiency is controlled by the magnetic configuration of the vortices, as confirmed by an analytical model highlighting the physics at play in the synchronization process as well as by micromagnetic simulations.

cond-mat.mes-hall↗

arXiv2015

Status of ArDM-1t: First observations from operation with a full ton-scale liquid argon target

ArDM-1t is the first operating ton-scale liquid argon detector for direct search of Dark Matter particles. Developed at CERN as Recognized Experiment RE18, the experiment has been approved in 2010 to be installed in the Spanish underground site LSC (Laboratorio Subterraneo de Canfranc). Under the label of LSC EXP-08-2010 the ArDM detector underwent an intensive period of technical completion and safety approval until the recent filling of the target vessel with almost 2 ton of liquid argon. This report describes the experimental achievements during commissioning of ArDM and the transition into a stage of first physics data taking in single phase operational mode. We present preliminary observations from this run. A first indication for the background discrimination power of LAr detectors at the ton-scale is shown. We present an outlook for completing the detector with the electric drift field and upgrade of the scintillation light readout system with novel detector modules based on SiPMs in order to improve the light yield.

physics.ins-det↗

arXiv2014

Electronic control of the spin-wave damping in a magnetic insulator

It is demonstrated that the decay time of spin-wave modes existing in a magnetic insulator can be reduced or enhanced by injecting an in-plane dc current, $I_\text{dc}$, in an adjacent normal metal with strong spin-orbit interaction. The demonstration rests upon the measurement of the ferromagnetic resonance linewidth as a function of $I_\text{dc}$ in a 5~$μ$m diameter YIG(20nm){\textbar}Pt(7nm) disk using a magnetic resonance force microscope (MRFM). Complete compensation of the damping of the fundamental mode is obtained for a current density of $\sim 3 \cdot 10^{11}\text{A.m}^{-2}$, in agreement with theoretical predictions. At this critical threshold the MRFM detects a small change of static magnetization, a behavior consistent with the onset of an auto-oscillation regime.

cond-mat.mes-hall↗

arXiv2006

Electrostatic Force Microscopy on Oriented Graphite Surfaces: Where Insulating and Conducting Behaviors Coexist

We present measurements of the electric potential fluctuations on the surface of highly oriented pyrolytic graphite using electrostatic force and atomic force microscopy. Micrometric domain-like potential distributions are observed even when the sample is grounded. Such potential distributions are unexpected given the good metallic conductivity of graphite because the surface should be an equipotential. Our results indicate the coexistence of regions with metallic and insulating behaviors showing large potential fluctuations of the order of 0.25V. We discuss the implications of these measurements in the disorder structure of graphite.

cond-mat.mes-hall↗

arXiv2006

Is there Ballistic Conductance Quantization in Real Life Metals Nanocontacts?

Theory and a vast set of experimental work in metals, since a century, appear to show that the mean free path of conduction electrons in a real metal is about the min (bulk mean free path, smallest transversal size of the metal), a result that was already proposed by J. J. Thomson in 1901. This establishes, as discussed in this work, serious difficulties to justify conductance quantization and ballistic transport in atomic/nanocontacts or nanoconstrictions of real life metals. The ohmic resistance of the leads proves to be as important as the ballistic one of the constriction.

cond-mat.mes-hall↗

arXiv2006

Spin injection in a single metallic nanoparticle: a step towards nanospintronics

We have fabricated nanometer sized magnetic tunnel junctions using a new nanoindentation technique in order to study the transport properties of a single metallic nanoparticle. Coulomb blockade effects show clear evidence for single electron tunneling through a single 2.5 nm Au cluster. The observed magnetoresistance is the signature of spin conservation during the transport process through a non magnetic cluster.

cond-mat.mtrl-sci↗

arXiv2002

Zero Permeability Materials (ZmuM): A way out of the "Left Handed Materials" trap

Recently it has been shown that due to losses the claims on observation of negative refraction using metamaterials are questionable. In this paper we discus an interesting case that is based in almost zero permeability at a given frequency: zero permeability materials. This represents a way out of the problem of left handed materials, and constitutes a material that acts a band pass filter with a very narrow band. The metamaterials claimed to present negative refraction are just showing this effect. However, absorption can be diminished in those metamaterials by using thicker wires. Materials based in quasi metallic magnetic structures are proposed with ferromagnetic resonance at microwave frequencies under applied magnetic fields. These materials, as well as the zero permitivity in thin films, open a new ground for a new set of optical devices.

cond-mat↗