Transport reversal in a delayed feedback ratchet

Feedback flashing ratchets are thermal rectifiers that use information on the state of the system to operate the switching on and off of a periodic potential. They can induce directed transport even with symmetric potentials thanks to the asymmetry of the feedback protocol. We investigate here the dynamics of a feedback flashing ratchet when the asymmetry of the ratchet potential and of the feedback protocol favor transport in opposite directions. The introduction of a time delay in the control strategy allows one to nontrivially tune the relative relevance of the competing asymmetries leading to an interesting dynamics. We show that the competition between the asymmetries leads to a current reversal for large delays. For small ensembles of particles current reversal appears as the consequence of the emergence of an open-loop like dynamical regime, while for large ensembles of particles it can be understood as a consequence of the stabilization of quasiperiodic solutions. We also comment on the experimental feasibility of these feedback ratchets and their potential applications.Comment: LaTeX, 7 pages, 6 figure

Threshold feedback control for a collective flashing ratchet: threshold dependence

We study the threshold control protocol for a collective flashing ratchet. In particular, we analyze the dependence of the current on the values of the thresholds. We have found analytical expressions for the small threshold dependence both for the few and for the many particle case. For few particles the current is a decreasing function of the thresholds, thus, the maximum current is reached for zero thresholds. In contrast, for many particles the optimal thresholds have a nonzero finite value. We have numerically checked the relation that allows to obtain the optimal thresholds for an infinite number of particles from the optimal period of the periodic protocol. These optimal thresholds for an infinite number of particles give good results for many particles. In addition, they also give good results for few particles due to the smooth dependence of the current up to these threshold values.Comment: LaTeX, 10 pages, 7 figures, improved version to appear in Phys. Rev.

Information and maximum power in a feedback controlled Brownian ratchet

Closed-loop or feedback controlled ratchets are Brownian motors that operate using information about the state of the system. For these ratchets, we compute the power output and we investigate its relation with the information used in the feedback control. We get analytical expressions for one-particle and few-particle flashing ratchets, and we find that the maximum power output has an upper bound proportional to the information. In addition, we show that the increase of the power output that results from changing the optimal open-loop ratchet to a closed-loop ratchet also has an upper bound that is linear in the information.Comment: LaTeX, 6 pages, 4 figures, improved version to appear in Eur. Phys. J.

Open Problems on Information and Feedback Controlled Systems

Feedback or closed-loop control allows dynamical systems to increase their performance up to a limit imposed by the second law of thermodynamics. It is expected that within this limit, the system performance increases as the controller uses more information about the system. However, despite the relevant progresses made recently, a general and complete formal development to justify this statement using information theory is still lacking. We present here the state-of-the-art and the main open problems that include aspects of the redundancy of correlated operations of feedback control and the continuous operation of feedback control. Complete answers to these questions are required to firmly establish the thermodynamics of feedback controlled systems. Other relevant open questions concern the implications of the theoretical results for the limitations in the performance of feedback controlled flashing ratchets, and for the operation and performance of nanotechnology devices and biological systems.Comment: LaTeX, 10 pages, 2 figures. Improved version to appear in Entrop

Out of equilibrium quantum field dynamics of an initial thermal state after a change in the external field

The effects of the initial temperature in the out of equilibrium quantum field dynamics in the presence of an homogeneous external field are investigated. We consider an initial thermal state of temperature T for a constant external field J. A subsequent sign flip of the external field, J to -J, gives rise to an out of equilibrium nonperturbative quantum field dynamics. The dynamics is studied here for the symmetry broken lambda(Phi^2)^2 scalar N component field theory in the large N limit. We find a dynamical effective potential for the expectation value that helps to understand the dynamics. The dynamics presents two regimes defined by the presence or absence of a temporal trapping close to the metastable equilibrium position of the potential. The two regimes are separated by a critical value of the external field that depends on the initial temperature. The temporal trapping is shorter for larger initial temperatures or larger external fields. Parametric resonances and spinodal instabilities amplify the quantum fluctuations in the field components transverse to the external field. When there is a temporal trapping this is the main mechanism that allows the system to escape from the metastable state for large N. Subsequently backreaction stops the growth of the quantum fluctuations and the system enters a quasiperiodic regime.Comment: LaTeX, 19 pages, 12 .eps figures, improved version to appear in Phys Rev

Escaneado de artefactos religiosos con un escáner de luz estructurada

[EN] The digitization process for religious artifacts is subject to inherent difficulties often ignored in theoretical models or pipelines. In this paper we aim to describe these problems, which are present in practical environments such as temples and churches, using white light scanners instead of other common devices or technologies such as laser scanners and photogrammetry. Our case study is based on the digitization of two religious statues belonging to a Catholic brotherhood located in a village of the Province of Jaén (Spain), one of them presenting especially several limitations. After performing the scanning process with a portable hand-held scanner, the images captured were processed until the final models were acquired. On the basis of the results obtained, we discuss the problems arising after using well-known procedures for the reconstruction of 3D models, their causes and some possible solutions to achieving a correct digitization. It should be noted that it is not the aim of this study to establish procedures for the digitization of religious artifacts, but rather to transmit the inherent constraints of these types of scenes.[ES] Los modelos teóricos de digitalización 3D no tienen en cuenta problemas de escenarios específicos como el de la digitalización de objetos religiosos. El objetivo de este artículo es describir estos problemas presentes en entornos prácticos como templos o iglesias usando un escáner de luz blanca en lugar de otros instrumentos o tecnologías comunes como los escáneres láser y la fotogrametría. Nuestro caso de estudio se basa en la digitalización de dos tallas religiosas pertenecientes a una cofradía de una localidad de la provincia de Jaén (España), siendo especialmente restrictiva una de ellas. Tras el procedimiento de escaneado llevado a cabo con un escáner de mano, las capturas se procesaron usando procedimientos clásicos de reconstrucción de modelos 3D hasta obtener los resultados finales. Basándonos en los resultados obtenidos realizamos una discusión de los problemas, causas y posibles soluciones para llevar a cabo una correcta digitalización. Cabe destacar que el objetivo del artículo más que establecer un flujo de trabajo es el de presentar las restricciones que presentan este tipo de entornos.This study has been partially supported by the Ministerio de Ciencia e Innovación and the European Union (via ERDF funds) under the research project TIN2014-58218-R, and by the University of Jaén through the research project UJA2015/08/10Graciano, A.; Ortega, L.; Segura, RJ.; Feito, FR. (2017). Digitization of religious artifacts with a structured light scanner. Virtual Archaeology Review. 8(17):49-55. doi:10.4995/var.2016.4650SWORD4955817Wang, K., Lavoué, G., Denis, F., & Baskurt, A. (2011). Robust and blind mesh watermarking based on volume moments. Computers & Graphics, 35(1), 1-19. doi:10.1016/j.cag.2010.09.01

A proposed testbed for detector tomography

Measurement is the only part of a general quantum system that has yet to be characterized experimentally in a complete manner. Detector tomography provides a procedure for doing just this; an arbitrary measurement device can be fully characterized, and thus calibrated, in a systematic way without access to its components or its design. The result is a reconstructed POVM containing the measurement operators associated with each measurement outcome. We consider two detectors, a single-photon detector and a photon-number counter, and propose an easily realized experimental apparatus to perform detector tomography on them. We also present a method of visualizing the resulting measurement operators.Comment: 9 pages, 4 figure

A New Cutting Device Design to Study the Orthogonal Cutting of CFRP Laminates at Different Cutting Speeds

[EN] Carbon Fiber-reinforced plastics (CFRPs) are widely used in the aerospace industry due to their highly mechanical properties and low density. Most of these materials are used in high-risk structures, where the damage caused by machining must be controlled and minimized. The optimization of these processes is still a challenge in the industry. In this work, a special cutting device, which allows for orthogonal cutting tests, with a linear displacement at a wide range of constant cutting speeds, has been developed by the authors. This paper describes the developed cutting device and its application to analyze the influence of tool geometry and cutting parameters on the material damage caused by the orthogonal cutting of a thick multidirectional CFRP laminate. The results show that a more robust geometry (higher cutting edge radius and lower rake angle) and higher feed cause an increase in the thrust force of a cutting tool, causing burrs and delamination damage. By reducing the cutting speed, the components with a higher machining force were also observed to have less surface integrity control.This research was funded by the Ministry of economy, Industry and Competitiveness and FEDER (grant number: DPI2017-89197-C2-1-R).Criado, V.; Feito-Sánchez, N.; Cantero Guisández, J.; Díaz-Álvarez, J. (2019). A New Cutting Device Design to Study the Orthogonal Cutting of CFRP Laminates at Different Cutting Speeds. Materials. 12(24):1-13. https://doi.org/10.3390/ma12244074S1131224Che, D., Saxena, I., Han, P., Guo, P., & Ehmann, K. F. (2014). Machining of Carbon Fiber Reinforced Plastics/Polymers: A Literature Review. Journal of Manufacturing Science and Engineering, 136(3). doi:10.1115/1.4026526Vigneshwaran, S., Uthayakumar, M., & Arumugaprabu, V. (2018). Review on Machinability of Fiber Reinforced Polymers: A Drilling Approach. Silicon, 10(5), 2295-2305. doi:10.1007/s12633-018-9764-9Panchagnula, K. K., & Palaniyandi, K. (2018). Drilling on fiber reinforced polymer/nanopolymer composite laminates: a review. Journal of Materials Research and Technology, 7(2), 180-189. doi:10.1016/j.jmrt.2017.06.003Wang, F., Yin, J., Ma, J., & Niu, B. (2018). Heat partition in dry orthogonal cutting of unidirectional CFRP composite laminates. Composite Structures, 197, 28-38. doi:10.1016/j.compstruct.2018.05.040Fernández-Pérez, J., Cantero, J. L., Díaz-Álvarez, J., & Miguélez, M. H. (2017). Influence of cutting parameters on tool wear and hole quality in composite aerospace components drilling. Composite Structures, 178, 157-161. doi:10.1016/j.compstruct.2017.06.043Feito, N., Díaz-Álvarez, J., López-Puente, J., & Miguelez, M. H. (2018). Experimental and numerical analysis of step drill bit performance when drilling woven CFRPs. Composite Structures, 184, 1147-1155. doi:10.1016/j.compstruct.2017.10.061López de Lacalle, L. N., & Lamikiz, A. (2009). Milling of Carbon Fiber Reinforced Plastics. Advanced Materials Research, 83-86, 49-55. doi:10.4028/www.scientific.net/amr.83-86.49Feito, N., Diaz-Álvarez, A., Cantero, J. L., Rodríguez-Millán, M., & Miguélez, H. (2015). Experimental analysis of special tool geometries when drilling woven and multidirectional CFRPs. Journal of Reinforced Plastics and Composites, 35(1), 33-55. doi:10.1177/0731684415612931Henerichs, M., Voß, R., Kuster, F., & Wegener, K. (2015). Machining of carbon fiber reinforced plastics: Influence of tool geometry and fiber orientation on the machining forces. CIRP Journal of Manufacturing Science and Technology, 9, 136-145. doi:10.1016/j.cirpj.2014.11.002Yan, X., Reiner, J., Bacca, M., Altintas, Y., & Vaziri, R. (2019). A study of energy dissipating mechanisms in orthogonal cutting of UD-CFRP composites. Composite Structures, 220, 460-472. doi:10.1016/j.compstruct.2019.03.090Lopresto, V., Langella, A., Caprino, G., Durante, M., & Santo, L. (2017). Conventional Orthogonal Cutting Machining on Unidirectional Fibre Reinforced Plastics. Procedia CIRP, 62, 9-14. doi:10.1016/j.procir.2016.07.036Santiuste, C., Olmedo, A., Soldani, X., & Miguélez, H. (2012). Delamination prediction in orthogonal machining of carbon long fiber-reinforced polymer composites. Journal of Reinforced Plastics and Composites, 31(13), 875-885. doi:10.1177/0731684412444654ZITOUNE, R., COLLOMBET, F., LACHAUD, F., PIQUET, R., & PASQUET, P. (2005). Experiment?calculation comparison of the cutting conditions representative of the long fiber composite drilling phase. Composites Science and Technology, 65(3-4), 455-466. doi:10.1016/j.compscitech.2004.09.028Rao, G. V. G., Mahajan, P., & Bhatnagar, N. (2007). Micro-mechanical modeling of machining of FRP composites – Cutting force analysis. Composites Science and Technology, 67(3-4), 579-593. doi:10.1016/j.compscitech.2006.08.010Wang, H., Chang, L., Mai, Y.-W., Ye, L., & Williams, J. G. (2018). An experimental study of orthogonal cutting mechanisms for epoxies with two different crosslink densities. International Journal of Machine Tools and Manufacture, 124, 117-125. doi:10.1016/j.ijmachtools.2017.10.003Lopresto, V., Caggiano, A., & Teti, R. (2016). High Performance Cutting of Fibre Reinforced Plastic Composite Materials. Procedia CIRP, 46, 71-82. doi:10.1016/j.procir.2016.05.079Voss, R., Seeholzer, L., Kuster, F., & Wegener, K. (2019). Analytical force model for orthogonal machining of unidirectional carbon fibre reinforced polymers (CFRP) as a function of the fibre orientation. Journal of Materials Processing Technology, 263, 440-469. doi:10.1016/j.jmatprotec.2018.08.001Seeholzer, L., Voss, R., Grossenbacher, F., Kuster, F., & Wegener, K. (2018). Fundamental analysis of the cutting edge micro-geometry in orthogonal machining of unidirectional Carbon Fibre Reinforced Plastics (CFRP). Procedia CIRP, 77, 379-382. doi:10.1016/j.procir.2018.09.040Feito, N., Diaz-Álvarez, J., López-Puente, J., & Miguelez, M. H. (2016). Numerical analysis of the influence of tool wear and special cutting geometry when drilling woven CFRPs. Composite Structures, 138, 285-294. doi:10.1016/j.compstruct.2015.11.065Cepero-Mejías, F., Curiel-Sosa, J. L., Zhang, C., & Phadnis, V. A. (2019). Effect of cutter geometry on machining induced damage in orthogonal cutting of UD polymer composites: FE study. Composite Structures, 214, 439-450. doi:10.1016/j.compstruct.2019.02.012Santiuste, C., Soldani, X., & Miguélez, M. H. (2010). Machining FEM model of long fiber composites for aeronautical components. Composite Structures, 92(3), 691-698. doi:10.1016/j.compstruct.2009.09.021Soldani, X., Santiuste, C., Muñoz-Sánchez, A., & Miguélez, M. H. (2011). Influence of tool geometry and numerical parameters when modeling orthogonal cutting of LFRP composites. Composites Part A: Applied Science and Manufacturing, 42(9), 1205-1216. doi:10.1016/j.compositesa.2011.04.023Iliescu, D., Gehin, D., Iordanoff, I., Girot, F., & Gutiérrez, M. E. (2010). A discrete element method for the simulation of CFRP cutting. Composites Science and Technology, 70(1), 73-80. doi:10.1016/j.compscitech.2009.09.007Wang, D., He, X., Xu, Z., Jiao, W., Yang, F., Jiang, L., … Wang, R. (2017). Study on Damage Evaluation and Machinability of UD-CFRP for the Orthogonal Cutting Operation Using Scanning Acoustic Microscopy and the Finite Element Method. Materials, 10(2), 204. doi:10.3390/ma10020204Sahraie Jahromi, A., & Bahr, B. (2010). An analytical method for predicting cutting forces in orthogonal machining of unidirectional composites. Composites Science and Technology, 70(16), 2290-2297. doi:10.1016/j.compscitech.2010.09.005Wang, D. H., Ramulu, M., & Arola, D. (1995). Orthogonal cutting mechanisms of graphite/epoxy composite. Part I: unidirectional laminate. 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High-Intensity Functional Training (HIFT): Definition and Research Implications for Improved Fitness

High-intensity functional training (HIFT) is an exercise modality that emphasizes functional,multi-joint movements that can be modified to any fitness level and elicit greater muscle recruitmentthan more traditional exercise. As a relatively new training modality, HIFT is often compared tohigh-intensity interval training (HIIT), yet the two are distinct. HIIT exercise is characterized byrelatively short bursts of repeated vigorous activity, interspersed by periods of rest or low-intensityexercise for recovery, while HIFT utilizes constantly varied functional exercises and various activitydurations that may or may not incorporate rest. Over the last decade, studies evaluating theeffectiveness of HIIT programs have documented improvements in metabolic and cardiorespiratoryadaptations; however, less is known about the effects of HIFT. The purpose of this manuscript is toprovide a working definition of HIFT and review the available literature regarding its use to improvemetabolic and cardiorespiratory adaptations in strength and conditioning programs among variouspopulations. Additionally, we aim to create a definition that is used in future publications to evaluatemore effectively the future impact of this type of training on health and fitness outcomes

Efficient generation of occlusion-aware multispectral and thermographic point clouds

The reconstruction of 3D point clouds from image datasets is a time-consuming task that has been frequently solved by performing photogrammetric techniques on every data source. This work presents an approach to efficiently build large and dense point clouds from co-acquired images. In our case study, the sensors coacquire visible as well as thermal and multispectral imagery. Hence, RGB point clouds are reconstructed with traditional methods, whereas the rest of the data sources with lower resolution and less identifiable features are projected into the first one, i.e., the most complete and dense. To this end, the mapping process is accelerated using the Graphics Processing Unit (GPU) and multi-threading in the CPU (Central Processing Unit). The accurate colour aggregation in 3D points is guaranteed by taking into account the occlusion of foreground surfaces. Accordingly, our solution is shown to reconstruct much more dense point clouds than notable commercial software (286% on average), e.g., Pix4Dmapper and Agisoft Metashape, in much less time (−70% on average with respect to the best alternative).Spanish Ministry of Science, Innovation and Universities via a doctoral grant to the first author (FPU19/00100)Project TED2021- 132120B-I00 funded by MCIN/AEI/10.13039/501100011033/ and ERDF funds ‘‘A way of doing Europe’