scholarly journals Estresse Térmico – os efeitos do calor sobre o desempenho físico

2018 ◽  
Vol 87 (4) ◽  
Author(s):  
Danielli Braga de Mello
Keyword(s):  
Thermal Stress ◽  
High Temperature ◽  
Physical Exercise ◽  
Physical Performance ◽  
Temperature Increase ◽  
Extreme Heat ◽  
Global Temperature ◽  
Prevention Strategies ◽  
Central Temperature ◽  
Outdoor Activities

Introdução: A temperatura global vem aumentando ao longo dos anos. Paralelo a isto, vem aumentando cada vez mais o número de praticantes em atividades outdoor. Sendo assim, torna-se essencial entender a fisiologia da termorregulação e os mecanismos de aumento datemperatura central para prever o risco de estresse térmico em ambientes quentes.Objetivo: O objetivo deste comentário foi refletir sobre os efeitos do calor na saúde e no desempenho físico, bem como apresentar as estratégias de reconhecimento e prevenção das doenças do calor.Conclusão: O ambiente extremo do calor influencia a saúde e o desempenho e a melhor forma de evitar os agravos à saúde e as doenças associadas à prática de exercício físico em ambientes de altas temperaturas climáticas é utilizar as estratégias de reconhecimento e prevenção.Thermal Stress - The Effects of Heat on Physical Performance Introduction: Global temperature has been increasing over the years. Parallel to this, the number of practitioners in outdoor activities has been increasing. Therefore, it is essential to understand the physiology of thermoregulation and the mechanisms of central temperature increase to predict the risk of thermal stress in hot environments.Objective: The purpose of this review was to reflect on the effects of heat on health and physical performance, as well as to present strategies for the recognition and prevention of heat illness.Conclusion: The extreme heat environment influences health and physical performance and the best way to avoid health problems and diseases associated with physical exercise in high temperature environments is to use recognition and prevention strategies.

scholarly journals Comparative study of the effectiveness of a low-pressure hyperbaric oxygen treatment and physical exercise in women with fibromyalgia: randomized clinical trial

2020 ◽  
Vol 12 ◽  
pp. 1759720X2093049
Author(s):  
Ruth Izquierdo-Alventosa ◽  
Marta Inglés ◽  
Sara Cortés-Amador ◽  
Lucia Gimeno-Mallench ◽  
Núria Sempere-Rubio ◽  
...  
Keyword(s):  
Physical Exercise ◽  
Physical Performance ◽  
Hyperbaric Oxygen ◽  
Functional Capacity ◽  
Pain Threshold ◽  
Cortical Excitability ◽  
Pressure Pain Threshold ◽  
Low Pressure ◽  
Pressure Pain ◽  
Perceived Pain

Background: Fibromyalgia (FM) is characterized by chronic pain and fatigue, among other manifestations, thus advising interventions that do not aggravate these symptoms. The main purpose of this study is to analyse the effect of low-pressure hyperbaric oxygen therapy (HBOT) on induced fatigue, pain, endurance and functional capacity, physical performance and cortical excitability when compared with a physical exercise program in women with FM. Methods: A total of 49 women with FM took part in this randomized controlled trial. They were randomly allocated to three groups: physical exercise group (PEG, n = 16), low-pressure hyperbaric oxygen therapy group (HBG, n = 17) and control group (CG, n = 16). Induced fatigue, perceived pain, pressure pain threshold, endurance and functional capacity, physical performance and cortical excitability were assessed. To analyse the effect of the interventions, two assessments, that is, pre and post intervention, were carried out. Analyses of the data were performed using two-way mixed multivariate analysis of variance. Results: The perceived pain and induced fatigue significantly improved only in the HBG ( p < 0.05) as opposed to PEG and CG. Pressure pain threshold, endurance and functional capacity, and physical performance significantly improved for both interventions ( p < 0.05). The cortical excitability (measured with the resting motor threshold) did not improve in any of the treatments ( p > 0.05). Conclusions: Low-pressure HBOT and physical exercise improve pressure pain threshold, endurance and functional capacity, as well as physical performance. Induced fatigue and perceived pain at rest significantly improved only with low-pressure HBOT. Trial registration: ClinicalTrials.gov identifier NCT03801109.

Investigation Into Thermal Stress Characteristics of Pipe-in-Pipe Under High Temperature Condition

2018 ◽  
Author(s):  
Si-Hwa Jeong ◽  
Min-Gu Won ◽  
Nam-Su Huh ◽  
Yun-Jae Kim ◽  
Young-Jin Oh ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Stress ◽  
High Temperature ◽  
Temperature Distribution ◽  
Heat Transfer Analysis ◽  
Piping System ◽  
Curved Pipe ◽  
High Temperature Condition ◽  
Single Pipe ◽  
Radiation Conditions

In this paper, the thermal stress characteristics of the pipe-in-pipe (PIP) system under high temperature condition are analyzed. The PIP is a type of pipe applied in sodium-cooled faster reactor (SFR) and has a different geometry from a single pipe. In particular, under the high temperature condition of the SFR, the high thermal stress is generated due to the temperature gradient occurring between the inner pipe and outer pipe. To investigate the thermal stress characteristics, three cases are considered according to geometry of the support. The fully constrained support and intermediate support are considered for case 1 and 2, respectively. For case 3, both supports are applied to the actual curved pipe. The finite element (FE) analyses are performed in two steps for each case. Firstly, the heat transfer analysis is carried out considering the thermal conduction, convection and radiation conditions. From the heat transfer analysis, the temperature distribution results in the piping system are obtained. Secondly, the structural analysis is performed considering the temperature distribution results and boundary conditions. Finally, the effects of the geometric characteristics on the thermal stress in the PIP system are analyzed.

scholarly journals Artificial Lightning Strike Tests and Coupled Electrical–Thermal Analysis on Roofing Glazed Tiles of Ancient Buildings

2021 ◽  
Author(s):  
Jingxiao Li ◽  
Zhiling Fang ◽  
Lin Fu ◽  
Shangchen Fu ◽  
Lihua Shi ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Thermal Stress ◽  
High Temperature ◽  
Heat Effect ◽  
Element Model ◽  
Joule Heat ◽  
The Body ◽  
Lightning Strike ◽  
Lightning Current ◽  
Lightning Channel

Abstract Lightning strike is one of the natural disasters to the roof components of ancient buildings. To investigate the causes and damage effects of lightning strikes on the roofing glazed tiles of ancient buildings, artificial lightning strike tests were carried out on glazed tiles. Based on the experiment results, a coupled electrical–thermal finite element model of mortar-containing glazed tiles was established and the Joule heat effect of lightning current was further investigated. The results show that when the lightning channel is attached to the surface of the enamel and body with a low electrical conductivity, the lightning current is mainly released in the form of surface flashover, and a minor damage is induced along the flashover path; when the lightning channel is attached to the mortar with a high electrical conductivity, the lightning current is injected into the mortar, resulting in significant tile damage. The spatial distributions of the temperature present clear gradient characteristics. The high-temperature area appears in the mortar while the high–thermal–stress area appears in the body connected to the grounding rail. As the peak of the lightning current increases, both the high-temperature and high–thermal–stress areas of the glazed tiles expand. The combination of the experiments and the numerical analysis results demonstrate that the damage mechanism of lightning Joule heat effect to glazed tiles may include two aspects. One is the internal explosive force generated from the sharp vaporization and expansion of the moisture inside the tiles due to rapid temperature increase, and the other is the thermal stress caused by the uneven temperature distribution.

Numerical Estimation of Flow Penetrating Depth Into Stagnant Branch Pipes for Thermal Fatigue Prediction

2014 ◽  
Author(s):  
Yoshihiro Ishikawa ◽  
Yukihiko Okuda ◽  
Naoto Kasahara
Keyword(s):  
Thermal Stress ◽  
High Temperature ◽  
Temperature Fluctuation ◽  
Thermal Stratification ◽  
Branch Pipe ◽  
Large Temperature ◽  
Bend Pipe ◽  
Main Pipe ◽  
High Temperature Water ◽  
Temperature Water

In the nuclear power plants, there are many branch pipes with closed-end which are attached vertically to the main pipe. We consider a situation in which the high temperature water is transported in the main pipe, the branch pipe is filled with stagnant water which has lower temperature than the main flow, and the end of the branch pipe is closed. At the branch connection part, it is known that a cavity flow is induced by the shear force of the boundary layer which separates from the leading edge of the branch pipe along the main pipe wall. In cases where the high temperature water penetrates into the branch pipe, there is a possibility that a steep and large temperature gradient field, called “thermal stratification layer” is formed at the boundary between high and low temperature water in the branch pipe. If the thermal stratification layer is formed in a bend pipe, which is used for connecting the vertical branch pipe and to a horizontal pipe, at the same time, the temperature fluctuation by the thermal stratification layer motion occurs, there may cause the thermal stress in the piping material. Furthermore, keeping the piping material under the thermal stress, there might be a possibility of a crack on the surface of the bend pipe. For this reason, the evaluation of the position where the thermal stratification layer reaches is very important during early piping design process. And, deeply understanding regarding the phenomena, is also important. However, because of the complexities of the phenomena, it is difficult to immediately clarify the whole mechanisms of the thermal stress arising due to the temperature fluctuation by the thermal stratification layer change. The complete prediction method for the position of the thermal stratification layer based on the mechanisms that is able to be applied to any piping system, any temperature and any velocity conditions, is also difficult. Therefore, a practical approach is required. The authors attempt to develop the practical estimation method for the thermal stratification layer position using the three-dimensional Navier-Stokes simulation which was based on the Reynolds-average in order to reduce the computational costs. In this paper, three different configurations of the piping were simulated and the simulation results were compared with the experimental results obtained by the other research group.

scholarly journals Pacific variability reconciles observed and modelled global mean temperature increase since 1950

2020 ◽  
Author(s):  
Martin B. Stolpe ◽  
Kevin Cowtan ◽  
Iselin Medhaug ◽  
Reto Knutti
Keyword(s):  
Global Warming ◽  
Temperature Change ◽  
Temperature Increase ◽  
Global Temperature ◽  
Global Mean Temperature ◽  
Mean Temperature ◽  
The Pacific ◽  
Global Warming Hiatus ◽  
Warming Hiatus ◽  
Global Mean

Abstract Global mean temperature change simulated by climate models deviates from the observed temperature increase during decadal-scale periods in the past. In particular, warming during the ‘global warming hiatus’ in the early twenty-first century appears overestimated in CMIP5 and CMIP6 multi-model means. We examine the role of equatorial Pacific variability in these divergences since 1950 by comparing 18 studies that quantify the Pacific contribution to the ‘hiatus’ and earlier periods and by investigating the reasons for differing results. During the ‘global warming hiatus’ from 1992 to 2012, the estimated contributions differ by a factor of five, with multiple linear regression approaches generally indicating a smaller contribution of Pacific variability to global temperature than climate model experiments where the simulated tropical Pacific sea surface temperature (SST) or wind stress anomalies are nudged towards observations. These so-called pacemaker experiments suggest that the ‘hiatus’ is fully explained and possibly over-explained by Pacific variability. Most of the spread across the studies can be attributed to two factors: neglecting the forced signal in tropical Pacific SST, which is often the case in multiple regression studies but not in pacemaker experiments, underestimates the Pacific contribution to global temperature change by a factor of two during the ‘hiatus’; the sensitivity with which the global temperature responds to Pacific variability varies by a factor of two between models on a decadal time scale, questioning the robustness of single model pacemaker experiments. Once we have accounted for these factors, the CMIP5 mean warming adjusted for Pacific variability reproduces the observed annual global mean temperature closely, with a correlation coefficient of 0.985 from 1950 to 2018. The CMIP6 ensemble performs less favourably but improves if the models with the highest transient climate response are omitted from the ensemble mean.

Improvement on Thermal Shock Resistance of Ceramic Components by Using Self-Healing

2010 ◽  
Author(s):  
Wataru Nakao
Keyword(s):  
Thermal Stress ◽  
High Temperature ◽  
Thermal Shock ◽  
Stress Fracture ◽  
Thermal Shock Resistance ◽  
Self Healing ◽  
Quenching Rate ◽  
Ceramic Components ◽  
Shock Resistance ◽  
Quenching Method

Availability of self-healing on the thermal shock resistance of ceramic components was investigated. Using gas quenching method, the crack-healed alumina-18 vol% SiC composite, which has excellent self-healing ability, was applied to thermal shock of the arbitrary quenching rate. The procedure could give rise to the thermal stress fracture at high temperature. The critical quenching rate at thermal stress fracture of the healed specimen was found to be 6.47 K/s, corresponding to the thermal stress of 452.3 MPa. Alternatively, that of the cracked specimen was found to be 5.02 K/s, corresponding to the thermal stress of 350 MPa. From the obtained results, usage of self-healing was confirmed to improve extremely thermal shock resistance. The present result suggests that usage of self-healing gives a large advantage to design the high temperature ceramic components, because the mechanically reliable design and thermal shock resistance cannot coexist due to low thermal conductivity.

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