Is it possible to create a thermal model of warm-up? Monitoring of the training process in athletic decathlon

The aim of the present study was to define if the athletes may vary their warm-up according to the specific demands of event they are preparing for and that higher-level athletes may differ in their thermal responses than lower-level athletes. Ten top level Polish male decathletes (19.9 ± 3.0 yr, 187.9 ± 4.7 cm, 82.7 ± 6.7 kg) who participated in the study were examined with a thermographic camera. Thermal imaging of each athlete was undertaken three times: at rest before the warm-up began, immediately after the general warm-up, and immediately after the specific warm-up.As significant changes in skin surface temperatures were observed between rest and both general and specific warm-ups (p < 0.001) it seems that athletes are able to vary their warm-up according to the decathlon event. Moving from rest to the general warm-up was characterized by decrease of the body surface temperature within the decathletes as a cohort. Interestingly, correlation was found between decathlon result measured by points and decrease of temperatures after commencing the general or specific warm-up exercises (r = 0.62; p < 0.05). However, the higher-performing competitors were characterized by a higher variability of skin temperatures depending on the event being prepared for.The present findings suggest that in sporting competitions characterized by the need for specificity of warm-up of different muscular segments, thermal imaging can be useful observe thermoregulatory responses. Due to these observed individual thermal reactions to the physical effort of warm-up, the present findings suggest it is possible to individually adapt the warm-up to the needs of both the event being prepared for and the level of athlete.     

Effect of training level and blood flow restriction on thermal parameters: Preliminary study

Training with blood flow restriction could lead to an effect on skin temperature. Additionally, this effect could be higher in people with lower physical fitness level due to their lower capacity of heat loss. The aim of this preliminary study was therefore to evaluate the effects of training experience on the acute and chronic thermal skin responses after performing exercise with and without blood flow restriction. The study included ten men, of these, five were trained. All subjects performed tests and re-tests for maximum strength (1 repetition maximum) through unilateral leg extensions (right thigh at 45 ± 6.7 kg and left thigh at 45.5 ± 8.1 kg, p > 0.05). The protocol consisted of four sets to concentric failure, with one-minute rest intervals between sets at an intensity corresponding to 40% of 1 RM. There were 7-day intervals between experimental sessions (150 mmHg versus unrestricted flow restriction). The thermal images were made before the protocol (pre), immediately after the end of the series (post), and 24 h afterward (post 24 h). When comparing temperature variation (Δ exercise and Δ 24 h) between groups, it was observed that the trained participants showed a greater drop in temperature 24 h after exercise with 150 mmHg restriction (confidence interval: 95% of Δ 24 h [−0.2 to −0.9 °C]) compared to untrained subjects (p = 0.006 and ES > 1.5, confidence interval: 95% Δ 24 h [−0.1 to 0.6 °C].) In conclusion, this preliminary study showed that training experience interferes with the chronic cutaneous thermal temperature of the anterior thigh when strength training associated with blood flow restriction 150 mmHg was performed.     

Investigation on interlaminar delamination tendency of multidirectional carbon fiber composites

In this investigation carbon fiber reinforced laminates with different orientation layups are prepared and studied under tensile loading condition. Multiple strain measurement techniques, namely, resistive strain gauges, embedded optical sensors and digital image correlation are used to analyze stress-strain behavior simultaneously through the thickness of composite materials, and to determine the sequence of failure in different plies. Inconsistencies of strains measured through different methods is correlated with the tendency for interlaminar delamination, therefore demonstrating the ability of multi-instrument approach to describe damage progress through the thickness of multidirectional laminates. Complementary analysis through acoustic emission methods reveals that the angle of off-axis surface plies can influence the sequence of failure under tensile loading condition, and damage monitoring capabilities of acoustic emission system is directly affected by delamination tendency of surface plies. Remarkably, the delayed failure of off-axis plies is shown to be related to reorientation of these layer towards loading direction using infrared thermography method.     

Quantitative temperature field measurements on a non-gray multi-materials scene by thermoreflectometry

This article addresses the problem of measuring an accurate temperature field on a multi-materials scene composed of two dielectric and one metallic materials. The measurements of thermo-radiative properties demonstrate that the scene exhibit very different emissivity spectra and thermal conductivities inducing high thermal gradients. From these radiative properties, the calculation of the theoretical temperature error of conventional passive methods highlights that a method may be suitable for measuring only one material but no method provides satisfactory measurements of the sets of materials. The proposed method, called thermoreflectometry, performs a simultaneous measurement on all materials thanks to an on-line indirect determination of emissivity based on a bidirectional reflectivity measurement. Its temperature error is compared to that of the selected passive method for each material through an experimental validation on the multi-materials scene. These results highlight the accuracy of thermoreflectometry and shows opening prospects for the on-line temperature control of dynamical processes.     

Deformation and dissipated energies for high cycle fatigue of 2024-T3 aluminium alloy

During the high cycle fatigue of aluminium alloys, an energy dissipation occurs. This dissipation is hard to be estimated because of the high diffusivity of such alloys and the importance of the thermoelasticity effects in comparison with others standard metallic materials (e.g., steels). Nevertheless the study of the energy balance gives valuable information about the nature of deformation mechanisms facilitating the construction of constitutive models associated with the microplasticity and damage of the aluminium alloy. In this work, the different energies involved in the energy balance were deduced from two complementary imaging techniques. The dissipation and thermoelastic sources were derived from an infrared thermography system, while the deformation energy was estimated from a digital image correlation system. Three tests with various loading blocks were carried out and a comparison between deformation and dissipation energies was systematically performed.     

热象无损检测技术应用

本文将热象无损检测技术应用于鉴定受测物结构和性质,并测出受测物中的缺陷,实验结果取得了较为满意的进展。     

细胞组织对称结构点温度漂移值诊断技术研究

体内细胞组织的缺陷能以皮肤表面所发射红外线的热效应，即细胞组织对称结构点温度漂移值诊断出来，分析缺陷温值的对称性并对其温度值的漂移量进行计算处理，可以临床确诊病变的准确部位。本文即介绍这一诊断系统。     

Asymptotic Formulas for Thermography Based Recovery of Anomalies

We start from a realistic half space model for thermal imaging, which we then use to develop a mathematical asymptotic analysis well suited for the design of reconstruction algorithms. We seek to reconstruct thermal anomalies only through their rough features. With this way our proposed algorithms are stable against measurement noise and geometry perturbations. Based on rigorous asymptotic estimates, we first obtain an approximation for the temperature profile which we then use to design nonit-erative detection algorithms. We show on numerical simulations evidence that they are accurate and robust. Moreover, we provide a mathematical model for ultrasonic temperature imaging, which is an important technique in cancerous tissue ablation therapy.AMS subject classifications: 35R20, 35B30     

Experimental investigation of a circular radially deforming cylinder near wake using an infrared technique

The present experimental study aims at developing a method to control the circular cylinder near wake by radial deformation and understand the underlying physics. Using an infra-red camera, we examine the temperature distribution of the near wake center line of a sinusoidal law radially deforming circular cylinder. From these measurements, the near wake is characterized by the length of the recirculation zone, the vortex formation zone length, the temperature fluctuation maximum intensity and the vortex street shedding frequency. For several deformations frequencies, we study the radial deformation influence on the near wake characteristics. It is noted that the wake structure is strongly affected by the deformation frequency. Among other things, we note the recirculation zone length reduction and the vortex formation zone length reduction when the radial vibrations are close to the “Lock-in” fundamental range. It is also noted that the variations of the vortex shedding frequency depend on the deformation frequency.     

利用红外热像技术快速预测材料的S-N曲线

研究材料疲劳一般采用试验的方法,但试验周期长, 所需试验试件和费用多,一直以来都是材料疲劳试验难以克服的困难,人们一直在探寻能快速得到材料疲劳性能的方法.本文在前人研究的基础上,采用红外热像技术,确定了材料的疲劳极限,并在"同种试件疲劳破坏消耗的塑性功不变"的假设下,通过建立塑性温升、热耗散、塑性功之间的关系给出了试件疲劳寿命的计算公式.由此经过简单的试验,理论上用一根试件,试验几个小时就可以快速确定材料的疲劳寿命,给出材料的S-N曲线.