Energy frictional dissipating algorithm for rigid and ellastic body’s contact problems

An Energy Frictional Dissipating Algorithm (EFDA) for time integration of Coulomb frictional impact–contact problems is presented. Using the Penalty Method, and in the context of a conserving framework, linear and angular momenta are conserved and energy is consistently dissipated. Published formulations were stable, forcing the energy dissipation to be monotonic in order to prevent unstable energy growth. The shortcoming of many was that they were not able to reproduce the real kinematics and dissipation of physical processes, provided by analytical formulations and experiments. EFDA formulates a conserving framework based on a physical energy dissipation estimator. This framework uses an enhanced Penalty contact model based on a spring and a dashpot, enforcing physical frictional energy dissipation, controlling gap vibrations and modifying the velocities and contact forces during each time step. The result is that the dissipated energy, kinematics and contact forces are consistent with the expected physical behavior

Angiogenesis in the Gonadal Capillary Network of the Chick Embryo

Seventy-one chick embryos of both sexes at the 35 Hamburger and Hamilton (H-H) developmental stage were processed for scanning electron microscopy of vascular corrosion casts and of critical point dried specimens, as well as transmission electron- and light microscopy, in order to study the angiogenic structures. The gonadal subepithelial capillary network was located at the level of the tunica albuginea under the covering epithelium. The casts showed a densely-meshed capillary network and numerous sprouting (nodular protrusions or capillary sprouts) and non-sprouting (enlarged vessels and angiogenic holes) angiogenic structures that were randomly distributed and mixed. Four types of angio-genic holes were encountered in the casts: primary (diameter \u3c 2.5 μm), secondary (diameter \u3e 2.5 μm), tertiary (variable diameter and circular narrowings on one side), and open angiogenic holes. We suggest that the different morphologies reflect evolution of these holes. Furthermore, the open angiogenic hole would probably either form nodular protrusions at its open ends, which tend to join with other nodular protrusions and neighboring capillaries and form new vessels; or there would be fusion with two or more neighboring open holes. Correlative critical point dried sections showed fenestrations in the capillary walls and transcapillary pillars that corresponded to the angiogenic holes found in the casts. Ultrathin sections of the vessels presented typical characteristics of growing endothelium: large nuclei with loosely textured chromatin, abundant cytoplasm rich in cell organelles and intraluminal endothelial processes

COMPRESSION PROFILE OF SPORT COMPRESSION STOCKINGS IN RUNNERS

The purpose of this study was to determine the interface pressure applied using two compressive stockings: medium compression (MC) and strong compression (SC); in three conditions: before, during and after running test. Ten male runners (n=10) exerted two laboratory test condition in different days: a) without compression stockings and b) with one kind of compression in each leg. Interface pressure was registered using PicoPress® device. In both compression conditions, the interface pressure was higher in proximal than distal sensors (MC p\u3c0,05; SC p\u3c0,001). Similar results were taken in dynamic condition, and lower level compression was observed after running test. In conclusion, compressive forces were higher in proximal compared to distal leg area. This is contradictory to the gradual decreasing compression principle

Reliability-based dynamical design of a singular structure for use in High Energy Physics experiments

[EN] The present work presents a comprehensive design and dynamic calculation of singular metallic structures, part of the Neutrino Experiment NEXT. The experiment uses an electroluminescent TPC chamber, a high-pressure 136Xe gas vessel enclosing the detector. A lead-block "castle'' or containing box shields this vessel against external g-rays from all directions; in spite of its heavy weight, the castle must be regularly open for the detector maintenance. Since the structures will be constructed at a middle-level seismic localization (Laboratorio Subterraneo Canfranc, Spain), the earthquake hazard must be taken into account. Vessel and castle are supported by a rigid frame, which must satisfy two requirements: (i) the Spanish seismic standard, (ii) for equipment protection, the detector maximum horizontal acceleration must be < 1 [m/s(2)]. This frame rests on special base isolators to decrease horizontal accelerations in case of an earthquake. Three dynamical calculations are conducted: (i) a response spectrum analysis to comply with the standard, (ii) five time-history analyses to calculate tolerances and, (iii) a reliability-based approach using 1000 timehistory responses to ensure satisfaction of the operating requirements. The final outcome is the design of a singular structure optimized for the NEXT experiment with a probability of failure against any standard earthquake of only 0.125%. (C) 2017 Politechnika Wroclawska. Published by Elsevier Sp. z o.o. All rights reserved.This research was supported by the grants CSD2008-00037 Canfranc Underground Physics.Palma, R.; Torrent, J.; Pérez-Aparicio, JL.; Ripoll, L. (2018). Reliability-based dynamical design of a singular structure for use in High Energy Physics experiments. Archives of Civil and Mechanical Engineering. 18(1):256-266. https://doi.org/10.1016/j.acme.2017.07.00325626618

DO SPORT COMPRESSION STOCKINGS IMPROVE COMFORT AND ACCELEROMETRY PARAMETERS IN RUNNERS?

In this study, we analysed accelerometry data from runners foot strikes with and without sport compression stockings. Also, we measured comfort perceived with these garments due its importance to a succesful performance. Ten male runners (n=10) exerted two laboratory test condition in different days: a) without compression stockings and b) with one kind of compression in each leg. Accelerometry data were registered using sensors in tibia and head. Also participants filled out a comfort test in stockings’ condition. Medium compression (MC) impacts attenuation was lower than no compression (NC) condition (p\u3c0,05). General comfort perceived was 66%. In conclusion, compression stockings demonstrated a protective effect against impacts and were perceived as comfortable

Vascular Architecture of the Lactating and Non-Lactating Teat of the Bitch: A Scanning Electron- and Light Microscope Study

Tissues from fourteen mammary glands of eight bitches were prepared for scanning electron microscopy of vascular corrosion casts and for histology to study the vasculature of the lactating and non-lactating teats. The densely-meshed mammary dermal capillary network formed ridges and troughs. The teat ducts were vascularized by a relatively densely-meshed capillary network which drained into veins longitudinally oriented to the ducts. Between eight and fifteen teat duct openings were seen on the tip of the teat, that were sometimes divided by a septum. The inner vascularization of the teat showed that the main papillary arteries divided into undulating secondary papillary arteries which presented numerous semi-constrictions and loops. Their structure may help during erection of the teat. Arteriovenous anastomoses found at different points may participate in blood flow maintenance during suckling, heat regulation and teat erection. Veins freely anastomosed and ran longitudinally to the axis of the teat. They exhibited numerous bicuspid valves. In non-lactating teats, vessels showed the same main architecture and characteristics mentioned above, although these were considerably less marked. The structure of the vascular elements in the teat of the bitch could favor blood flow during suckling and suggest that vessels adapt to the physiological situation

Simultaneous and accurate measurement of the dielectric constant at many frequencies spanning a wide range

We present an innovative technique which allows the simultaneous measurement of the dielectric constant of a material at many frequencies, spanning a four orders of magnitude range chosen between 10 --2 Hz and 10 4 Hz. The sensitivity and accuracy are comparable to those obtained using standard single frequency techniques. The technique is based on three new and simple features: a) the precise real time correction of the amplication of a current amplier; b) the specic shape of the excitation signal and its frequency spectrum; and c) the precise synchronization between the generation of the excitation signal and the acquisition of the dielectric response signal. This technique is useful in the case of relatively fast dynamical measurements when the knowledge of the time evolution of the dielectric constant is needed

Optimization of pulsed thermoelectric materials using simulated annealing and non-linear finite elements

[EN] The objective of this work is to determine the optimal shape, gains and duration of an electric pulse applied to a Peltier cell, together with the length of the thermoelectric to maximize cooling while min- imizing electric consumption. For this purpose, a fully coupled, multiphysics, dynamic finite-element model, which solves for the thermal, electric and mechanical fields is used. Because of the demanding computing requirements of the optimization process, a special mesh is designed and a convergence anal- ysis is carried out before using the multiphysics model. The highly non-linear optimization is done by simulated annealing, a heuristic algorithm in the Markov chain Monte-Carlo family. A preliminary para- metric investigation is presented, analyzing the impact of some of the parameters. The results of this pre- liminary analysis help to understand the effect of the different shapes in the evolution of the cold face temperature. Some of these results are expected and have already been discussed elsewhere, but others can only be explained after further analysis and a full system modeling. Pulse optimization is multiobjec- tive and multiparametric, i.e., it can consider several targets such as maximizing the cooling temperature, the cooling duration or others. The trade-offs between the different targets are studied. In all cases, stres- ses inside the thermoelement are examined at all points, and the pulses must meet the restriction that an equivalent stress is not above the allowable value.This research was partially supported by the grants, Haut-de-France Region (CR Picardie, 120-2015-RDISTRUCT-000010), EU funding (FEDER, RDISTRUCT-000010) for Chaire-de-Mecanique, and Spanish Ministry of Economy and Competitiveness grant CGL2014-59841-P. These supports are gratefully acknowledgedMoreno-Navarro, P.; Pérez-Aparicio, JL.; Gómez-Hernández, JJ. (2017). Optimization of pulsed thermoelectric materials using simulated annealing and non-linear finite elements. Applied Thermal Engineering. 120:603-613. https://doi.org/10.1016/j.applthermaleng.2017.04.036S60361312

Analytical and multicoupled methods for optimal steady-state thermoelectric solutions

[EN] Peltier cells have low efficiency, but they are becoming attractive alternatives for affordable and environmentally clean cooling. In this line, the current article develops closed-form and semianalytical solutions to improve the temperature distribution of Bi2Te3 thermoelements. From the distribution, the main objective of the current work-the optimal electric intensity to maximize cooling-is inferred. The general one-dimensional differential coupled equation is integrated for linear and quadratic geometry of thermoelements, under temperature constant properties. For a general shape, a piece-wise solution based on heat flux continuity among virtual layers gives accurate analytical solutions. For variable properties, another piece-wise solution is developed but solved iteratively. Taking advantage of the formulae, the optimal intensity is directly derived with a minimal computational cost; its value will be of utility for more advanced designs. Finally, a parametric study including straight, two linear, barrel, hourglass and vase geometries is presented, drawing conclusions on how the shape of the thermoelement affects the coupled phenomena. A specially developed coupled and non-linear finite element research code is run taking into account all the materials of the cell and using symmetries and repetitions. These accurate results are used to validate the analytical ones.This work was supported by the Generalitat Valenciana research programmes PROMETEO/2020/016: Applications de Topologic Isolators in Spintronics and Thermoelectricity (TOP-TERM) and BEST/2021/079. The support is gratefully acknowledged.Moreno-Navarro, P.; Pérez-Aparicio, JL.; Gómez-Hernández, JJ. (2022). Analytical and multicoupled methods for optimal steady-state thermoelectric solutions. Coupled Systems Mechanics, an international journal. 11(2):151-166. https://doi.org/10.12989/csm.2022.11.2.15115116611

Assessment of a Global-to-Direct empirical model for the long-term characterization of Direct Normal Insolation

The statistical characterization of the solar resource (direct normal solar radiation) is a key point in the initial phases of a solar thermal electricity (STE) plant project. Ideally, this characterization should be based on long time series (at least 8 years) of on-site measured data of Direct Normal Insolation (DNI) and other meteorological parameters. Unfortunately, there are very few places around the world where such time series are available, so alternative methods have to be used. Most of them rely on the application of global-to-direct conversion models to long time series of Global Horizontal Insolation (GHI), measured or derived from satellite images, to estimate the long-term resource. Usually, a meteorological station including sensors for the measurement of DNI is installed at the selected project site at the beginning of the project. The data collected during the measurement campaign, which normally extends between a few months and 2 years, are used to adjust the conversion models and to correct the estimates. In this paper, a simple empirical model that relates monthly clearness index and monthly direct normal fraction is used to estimate monthly and annual long-term DNI from statistically representative monthly values of GHI. This model is adjusted with GHI and DNI data collected during measurement campaigns of different durations. We show that the accuracy of the proposed model is under +-5% and that this accuracy improves sharply with the duration of the test campaign. For this purpose, we have used 13 years of high quality DNI and GHI data from the radiometric station of the Group of Thermodynamics and Renewable Energies (GTER) of the University of Seville, Spain. The results suggest that, this simple empirical model is a good alternative to the present methodologies when short DNI measurement campaign but long-term GHI values are available