This study analyzed an atmospheric corrosion sensor using strain measurements (ACSSM) with an active dummy method for corrosion product experiments. An initial compensation thermal strain experiment ...was performed with elapsed time. Further analyses used dry-wet environments with salt water spray to investigate the thickness reduction performance of the corrosion product on low-carbon steel samples. The ACSSM with an active dummy method accurately measured signals induced by the specimen thickness reduction, despite the noise in the signal. Moreover, the effects of corrosion products on the signal were discussed.
During acclimatization to heat and cold, the body experiences additional thermally induced physiological strain. The first signs show up in the respiratory organs because respiration is a continuous ...heat exchange process in which the body is in closest contact with the ambient air. There are no behavioral or other adjustments to prevent the ambient air from entering into the body’s core area through the respiratory tract. The Acclimatization Thermal Strain Index (ATSI) describes the acclimatization thermal loading (ATL) on respiratory organs until full adaptation is achieved. The aim here is to further assess the ATSI scheme using a range of actual but contrasting bioclimatic conditions. To simulate ATL, scenarios of the consequences of acclimatization due to movement to or from five contrasting climates are used. The results show that adjusting to cold comes with greater physiological strain than adjusting to heat, the biggest impact occurring for a change of location from hot-humid to cold-dry climatic conditions. The approach can be used to assess risks due to increases in short-term thermal variability in weather conditions such as encountered during heat waves and cold snaps. The information could also be useful for assessing the need for public health services and measures that might be used to help mitigate impacts.
High transmittance and low birefringence are desirable optical properties in polyimide films which are promising flexible substrates in next generation display devices. However, thermal processes for ...the fabrication of polyimide films can cause anisotropic changes in the optical properties due to its rod-like molecular structure. Here we report the changes in optical retardation in transparent fluorinated polyimide films with sub-nanometer resolution and dimensional stability induced by deformation at high temperatures. As deformation is increased, the optical retardation is changed much prominently with enhancing thermo-dimensional stability. During thermal strain, in-plane molecular orientation is preferentially improved and stress-optical coefficient that quantifies the change in out of plane optical retardation is derived to be around 6×10
–6
m
2
/N, which is higher compared to conventional plastic optical films. The experimental findings suggest that optimized process conditions for display substrates should be determined to address both changes in the optical and thermal stabilities. We suggest that this study can be useful information for large-scale film process to be further utilized in fabrication of the transparent polyimide films.
It is known that warm and humid environment reduces human physical performance. The present study examined whether the use of an ice-vest in such conditions can improve cycling performance.
Seven ...participants cycled with consecutive, non-stop, 10-minute cycles of nine minutes at 60% of their
V
̇
O
2
max punctuated by a one-minute sprint at 80%
V
̇
O
2
max. The cycling protocol was continuously repeated until exhaustion. The protocol was performed with the ice-vest (ICE), worn after 30
min of cycling, and without the ice-vest throughout the protocol (CON). Ventilatory and thermal responses were continuously recorded. Electromyographic (EMG) signals from four muscles of the dominant leg were recorded over one minute, and subjective sensations were evaluated at 10-minute intervals. At exhaustion, the exercise time was recorded.
Exercise time improved significantly while wearing the ice-vest from 61
min and 29
s to 74
min and 14
s (+21.5%±7.6;
p<0.05). Mean power frequency and amplitude of the EMG revealed decreased neuromuscular fatigue during ICE compared to CON. Ventilatory responses indicated a tendency towards lower ventilation, respiratory quotient was significantly lower and both thermal parameters and subjective sensations indicated lower thermal strain during ICE in comparison to CON.
These results suggest that wearing an ice-vest during cycling in warm and humid conditions decreases thermal and physical strain, thereby improving cycling performance.
Purpose
The aim of this study was to analyze the physiological demands and thermal strain of wildland firefighters during real wildfire suppression.
Methods
The response of core temperature and heart ...rate (HR) were analyzed in 200 wildland firefighters during wildfire suppression activities of different duration: <1 h (
n
= 52), 1–3 h (
n
= 70), 3–5 h (
n
= 44), and >5 h (
n
= 34). The exercise workload (TRIMP), the physiological strain index (PSI), and cumulative heat strain index (CHSI) were calculated using the time spent in different intensity zones, the HR, and core temperature.
Results
Mean HR was significantly higher (
P
< 0.05) in wildfires <1 h (133 ± 2 bpm) and 1–3 h (128 ± 1 bpm) versus 3–5 h (120 ± 3 bpm) and >5 h (116 ± 32 bpm). The time spent in higher intensity zones increased (
P
< 0.05) when wildfire duration increased. TRIMP accumulation increased with wildfire duration (54.9 ± 3.2, 167.4 ± 5.9, 296.0 ± 8.3, 511.7 ± 12.8 in <1, 1–3, 3–5, and >5 h, respectively). Neither core temperature (37.4 ± 0.1°C) nor PSI (4.5 ± 0.2) were influenced by wildfire duration. The CHSI increased (
p
< 0.05) in the following order: <1 h (104 ± 23), 1–3 h (1,396 ± 275), 3–5 h (4,586 ± 387), and >5 h (10,703 ± 710).
Conclusions
The results demonstrate the high work strain sustained by Spanish wildland firefighters during wildfire suppression. Both workload and CHSI increased with the wildfires duration although the pace of work was faster in wildfires of a shorter duration.
Sultriness is a specific case in thermal perception under warm/humid environments and frequently applied in German operational weather forecast and is assumed if the dew-point temperature
t
d
exceeds ...a threshold of 16.5 °C. In perceived temperature (
PT
), which is based on the ASHRAE two-node-model, a Central European climatology was prepared of the classical predicted mean vote (
PMV
), exclusively linked to thermal stress, and the so-called rational
PMV
* that additionally accounts for the humidity in the meteorological environment and is closely linked to thermal strain. The standard deviation of the difference Δ
PMV
=
PMV
* −
PMV
over
PMV
reveals a similarity to the appearance of sultriness that suggests as side effect of the
PT
parameterisation a thermophysiologically based definition of sultriness: “Under warm/humid conditions a subject adapted to mild climatologic conditions perceives sultriness if the actual value of Δ
PMV
exceeds the long-term mean by more than its single standard deviation”. This definition accounts for all environmental and subject related variables influencing the thermal state of the body and is in accordance with all in the literature described properties in the perception of sultriness. The two definitions coincide more or less at daylight hours for
t
d
values markedly beyond the threshold. However, in the
t
d
threshold region, the
PT
-derived definition offers stronger differentiated patterns and is significantly less frequent at nighttime than the mono-causal definition. For given
PT
values, the sensible heat flux via the skin shows an increase under a sultry environment, whereas the latent is reduced; skin and core temperatures as well as the skin blood flow are also less. In any case,
PT
-derived sultriness is linked with an increased thermal strain on the body temperatures, which is a measure of discomfort caused by increased humidity and/or dissatisfaction with the thermal environment. This confirms the thermal uncomfortable feeling accompanying the perception of sultriness. Therefore, the
PT
-derived sultriness can be presumed to be a more appropriate measure for the perception of sultriness, because it accounts for all environmental impacts on thermoregulation.
When concrete is heated under a sustained load, a large amount of shrinkage occurs to compensate for thermal for expansion. This shrinkage was termed the load-induced thermal strain (LITS), and must ...be considered when performing a deformation analysis of reinforced concrete structures that are subjected to fire. In the constitutive strain models used in such analyses, the LITS is a function of the concrete temperature. However, the relationship between the LITS and temperature is influenced by the water of the concrete, making it difficult to apply these models to concrete with different water conditions. In the present study, the influence of the curing conditions (air-dried, oven-dried and sealed curing) and water/cement ratios (40%, 50% and 65%) on the LITS was investigated based on results obtained from the transient tests for measuring total thermal strain of concrete specimens. The relationship between the LITS and specimen weight loss was also evaluated in order to develop a comprehensive model for the LITS that is appreciable to concrete with different curing conditions and water/cement ratios. In the transient tests for measuring total thermal strain, specimens ware heated at a constant rate of 1.5 degree C/min. up to 800 degree C under constant load. The ratio of the constant load to compressive strength of air-dried specimens at room temperature was settled between 0.1 and 0.7. The LITS was calculated by subtracting value of the free thermal strain from the total thermal strain. The heating rate in the transient tests for measuring the weight loss was same as the tests of the total thermal strain. The main results obtained from the present study are as follows: (1) The influence of the water evaporation on the LITS was evident between 100 degree C and 200 degree C. (2) The influence of the dehydration and decomposition of the cement hydrate on the LITS was evident above 200 degree C. (3) The LITS due to dehydration and decomposition was larger than that due to water evaporation. (4) The relationship between the LITS and load level was seen to be linear, regardless of the curing conditions or water/cement ratio. (5) The numerical model for the LITS was proposed as a function of the weight loss of the specimens. And, it was indicated that the proposed model could be appreciable to concrete with different curing conditions and water/cement ratios.
New improved austenitic steel NF 709 was studied in term of thermal and radiation stability in consideration of its application as structural material for the newest generation of nuclear reactors – ...Generation IV. Samples of steel NF 709 were exposed to two strains: annealing at 1000°C in argon atmosphere and simulated irradiation performed by helium ion implantation. Changes of the microstructure after the experimental strains were observed by positron annihilation techniques. The microstructure after both treatments indicated growing of vacancy defects; although these changes were small or in the range of error bar. Thus, material NF 709 can be considered as well resistant to these applied strains.
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