Increase In Ambient Temperature Research Articles

Influencing factors of lithium-ion battery thermal runaway in confined space

Lithium-ion batteries with high state of charge (SOC), low state of health (SOH) and at summer are prone to fire accidents. The influence of these factors on thermal runaway triggered by external heating in confined space is studied in this manuscript. Based on the results of temperature, voltage changes and video, gas explosion occurs before thermal runaway in confined space. The results of heat calculation indicate that radiation and conduction contribute the most to thermal runaway. Thermal runaway of lithium-ion battery triggered by external heating is determined by the accumulated exothermic side reactions, remaining reactants and surface temperature of battery. Accumulated exothermic side reactions increase with higher SOC and lower SOH. Remaining reactants increase with the increase of SOC and SOH. Surface temperature of lithium-ion battery increases to high temperature at a shorter time for battery at higher initial temperature. Thermal runaway time interval decreases with the increase of SOC and ambient temperature, and the decrease of SOH. High SOC and ambient temperature and low SOH increase hazardous risk of lithium-ion battery to some extent. The results can explain why batteries with high SOC, low SOH and at high ambient temperature are prone to fire accidents. This is important for battery safety control.

Effect of ambient temperature and wind speed on horizontal flame spread and combustion trace on typical decorative wood boards

Decorative wood boards are common combustible materials and have been utilized in lots of buildings, which could bring serious property loss and casualties due to fires. In order to analyze fire hazard of decorative wood boards, horizontal flame spread characteristics and combustion traces were studied on six typical decorative wood boards though the tunnel furnace test in this paper. It was found that the flame spread distance of all the samples were in power function with time. With the increase of ambient temperature and ambient wind speed, the combustion was more intense, the crack length increased, the flame spread distance, and the flame spread rate (V) all increased, the cracks got wider, the micro appearance damage and the degree of carbonization got more serious. Among them, the relationship between V and the initial temperature difference (Tv-Ti) between solid pyrolysis temperature and the ambient temperature could be expressed as V∼(Tv-Ti)θ and the exponent of the power law θ was −6.24 for the decorative wood boards; the relationship between V and the ambient wind speed (U∞) could be expressed as V ∼ U∞δand δ was 9.0 for the decorative wood boards. In addition, the change rules of C, P and S elements on the combustion residues were similar, which were opposite to the change rule of O.

Effect of climate change on the behaviour of thermo-active diaphragm walls

Energy geo-structures are becoming more common as a renewable energy solution which utilises shallow geothermal energy to provide heating and cooling to buildings and civil infrastructure projects. There has been an upward trend in the use of thermo-active geo-structures in the United Kingdom, from 150 in 2005 to over 5000 in 2012 [2]. Studies so far have shown that diaphragm walls subjected to combined thermo-mechanical loading show overall increases in lateral displacements, bending moments, shear forces, axial forces, and settlements on the retained side with thermal cycles [6, 7, 8].
 This study uses a variation of a validated numerical model [4] to predict the behaviour of thermo-active diaphragm walls in the longer-term including accounting for the influence of climate change. This numerical model also assesses the impact of different modelling assumptions on the model output by comparing a simplified model with a more complex model where atmospheric temperatures affecting ground surface temperatures are included. Research from the IPCC shows increases in ambient temperatures and in maximum extreme temperatures as a result of climate change. Two models are compared in the IPCC report [5], Representative Concentration Pathway (RCP) 2.6 where governments across the world work together to meet the recommendations in the report to reduce overall warming, and RCP8.5 where the current trends of heating continue without any governmental interventions. According to climate model RCP2.6, global mean surface air temperatures will increase by around 1.5°C and extreme daily temperatures (i.e. days where temperatures exceed expected temperatures for the time of year) will increase by around 2°C over the 50-year period chosen for this study, whilst using RCP8.5 global mean surface air temperature increases by approximately 3°C and extreme daily temperatures increase by approximately 5°C.
 This study uses the same model geometry as a model validated through centrifuge testing [4] which is a 5m deep cantilever diaphragm wall, like those that would be used in deep excavations for open-topped tunnels in large civil infrastructure projects. The numerical model was developed using the semi-coupled thermo-hydro-mechanical (THM) thermal module available with PLAXIS 2D and uses the HS-Small soil model [3] to allow for variation in shear modulus at small strains (i.e. those associated with retaining walls) to be captured more accurately. Thermal loads were applied by applying heat flows through a plate element with the same mechanical properties of the model diaphragm wall used in centrifuge testing. This model attempts to capture the influence of atmospheric temperatures by applying thermal boundary conditions to the ground surface as well as to the thermo-active diaphragm wall. Studies have demonstrated that a more complex model capturing atmospheric temperatures increases the impact of thermal loading [4], whilst also capturing a more realistic temperature profile throughout the entire depth of the soil body both adjacent to the wall and in the free field condition. In this study, atmospheric temperatures were captured in RCP2.6 by cycling between 30°C and -5°C over the course of the cycle to represent a typical ‘hottest’ and ‘coldest’ day of the year in cycle 1, increasing to 32°C and -5°C in line with the temperature increases described in the IPCC report [5]. Ambient mean temperatures between heating and cooling cycles increased from 20°C to 21.5°C over the 50-year period. In the same model, the temperature within the diaphragm
 wall cycled between 35°C and 10°C in cycle 1, representing the typical operation of a ground source heat pump (GSHP) in heating and cooling. These temperature inputs increased to 37°C and 10°C over the 50-year period. The RCP8.5 atmospheric temperatures cycled between 30°C and -5°C to represent summer and winter in cycle 1 and increase to 35°C and -5°C over the 50-year period. Thermal flows in the diaphragm wall cycled between 35°C and 10°C in cycle 1 and increased to 40°C and 10°C over the 50-year period. The results from this study show increases in lateral displacement, maximum bending moments, positive and negative shear forces and axial forces (compressive (-) and tensile (+)). These results are shown in Figure 1.
 Significantly, the RCP2.6 model shows that these increases begin to stabilise over the 50-year period, with the increases in the final cycles becoming negligible. With the RCP8.5 model these increases are increasing linearly at the end of the modelling period which can potentially have significant implications not only in terms of serviceability of the structure, but potentially on ultimate limit state as linear increases suggest that design limits will eventually be reached. The findings from this study generally agree with other similar studies, such as a study that analysed the geotechnical performance of energy piles with additional environmental loading as a result of climate change which found that additional compressive and tensile stresses are generated during heating and cooling phases, respectively [1].

High-precision Low-power Low-temperature Drift Dropout Voltage Cancellation Oscillator

As electronic products continue to develop, the requirements for the accuracy of integrated circuits continue to increase. Oscillators play a more important role in integrated circuits, and higher requirements are placed on the power consumption as well as the accuracy of oscillators. In this paper, a high-precision and low-power consumption RC oscillator is designed. The oscillator in this paper consists of a bias module and a capacitor charging and discharging module and provides bias current and voltage with temperature coefficient through bandgap to reduce the change of oscillator operating frequency caused by the increase of ambient temperature in traditional oscillators, which improves the oscillator operating state under different temperatures and the accuracy of the oscillator. The single comparator oscillator structure is also designed to effectively eliminate the effect of the dropout voltage on the oscillation period. The oscillator is simulated by using the MGN 0.18 μm process.

Drinking water intake, milk production, and grazing behaviour of alpine dairy goats in response to daytime water restriction on temperate pastures

Certain local breeds of goats have adapted to severe water restriction in arid and semi-arid regions, but little is known about the adaptability of high-producing dairy goats to water restriction while grazing under temperate conditions. The aim of this study was to assess effects of water restriction of lactating Alpine goats during the daytime at pasture (8 h/d) on herd-level drinking water intake and individual milk production and grazing time. Goats remained in the barn between evening and morning milkings, where each animal was offered 600 g of concentrate and 400 g of hay each day, with free access to water. Twenty four goats were used in a crossover design, for two consecutive 14-d periods. The study was conducted in early summer, with a daily mean ambient temperature of 18.2 ± 3.5 °C (range of 13–27 °C over all the study days), a mean temperature-humidity index of 64 ± 4.9 (range of 56–76). Goats had access to a high-quality multispecies pasture with a mean of 216 ± 44 g DM/kg fresh matter. Total drinking water intake averaged 5.57 L/d and did not differ significantly between treatments. Goats with water access at pasture drank a mean of 1.88 L of water per day during the grazing period, but drank 2.24 L less per day in the barn than goats without water access at pasture. Drinking water intake increased by 0.57 L per day for each °C increase in daily mean ambient temperature. Daily milk production, milk composition, body weight, and daily grazing time did not differ between treatments. Only the duration of the first morning meal at pasture differed significantly between treatments. Thus, water restriction for 8 h per day during grazing periods does not seem to influence the variables measured for Alpine dairy goats under temperate conditions.

Increased <i>Arabidopsis thaliana</i> cell culture resistance to sodium fluoride by constitutive expression of HSP101

Fluorine is one of the toxic elemental components of industrial emissions. Increased fluoride content in the atmosphere, soil or water negatively affects the growth and development of plants, as well as reducing resistance to various environmental stressors. An increase in ambient temperature causes a protective response in all organisms taking the form heat shock protein synthesis. The specific protein HSP101, which performs the function of protecting plant cells from heat damage, is also responsible for inducible thermotolerance, representing the ability of organisms to withstand the effects of severe heat shock that were previously exposed to mild heat stress, as a result of which heat shock proteins are induced. Heat shock proteins are involved in protecting not only against elevated temperatures, but also various other stress factors. In this work, the effect of sodium fluoride treatment on the viability of Arabidopsis thaliana cell culture, expression and synthesis of heat shock proteins was studied along with the role of heat shock protein HSP101 in providing resistance to fluoride. Sodium fluoride has been shown to significantly reduce the viability of A. thaliana cells by suppressing the activation of HSP101 gene expression with an increase in temperature. At the same time, the A. thaliana line, which has constitutive expression of the HSP101 gene, proved to be more resistant to the toxic effects of sodium fluoride.

A-187 The Effect of Ambient Temperature on Potassium During Hot Months: The Seasonal Pseudohypokalemia Delima!

Abstract Background Laboratory tests are vital tools for the clinicians and it is becoming more and more the most the decision maker for the management of patients. Blood samples are drawn from patients and transported to the laboratory for analysis; samples are exposed to various temperatures during transportation which could have an effect on test results. We studied the effect of seasonal change on the potassium results using lithium heparin plasma tubes. Method We compared the results collected from one day/month each from January 2022 to August 2022 from patients residing in Long-Term Care Facilities and were transported to the laboratory during which the samples were exposed to ambient temperature. A total of 16 086 specimens were collected using Lithium heparin plasma tubes up to 8/8/2022, sample on 8/15/22 were collected using serum gel separation tubes. Statistical analysis was done using Analyse-it. Results our results showed an increase in hypokalemia with the increase in ambient temperature, the highest incidence of hypokalemia was during the month of June to August which corresponds with the higher ambient temperature. There was an increase in hypoglycemia at the same time of the increase in hypokalemia. The percentage of samples with hypokalemia was normalized when serum (SST) tubes were used. Conclusion Seasonal pseudohypokalemia is phenomena that is seen when the samples are transported to the laboratory from different collection sites during the hot temperature. The increase in hypokalemia could be due to an increase in glucose metabolism and the cellular uptake of potassium or could be mediated by sodium-potassium-exchange-ATPase. Serum samples were less affected by the temperature change than lithium heparin plasma. It is very important to emphasis on the temperature during transporting samples to the laboratory to avoid seasonal pseudohypokalemia in the hot temperature season and hyperkalemia during the cold temperature season.

Experimental study on heat transfer during melting in metal and carbon foam saturated with phase-change materials for temperature control in electronic devices

Porous media embedded in phase-change materials (PCMs) have been widely applied to thermal management of electronic devices, whereas the influence mechanisms of the suppression of the natural convection of liquid PCM by the porous skeleton and anisotropy of the skeleton on the temperature response of the heat source are still unclear. In this study, an isotropic metal foam and several anisotropic carbon foams are embedded in paraffin and higher alcohol, respectively. The influences of copper-foam skeleton on the PCM natural convection, the evolution of PCM melting front, and the variation of heat-source temperature are studied. The effects of carbon-foam skeleton on the directionality of phase-change heat transfer and the variation of heat-source temperature are investigated. The embedding of metal foam can reduce the heat-source temperature, postpone the onset of PCM melting and the appearance of natural convection, and shorten the PCM melting duration mildly. The anisotropy of carbon foams causes the out-of-plane thermal conductivities of carbon-foam/PCM composites to be larger than the in-plane thermal conductivities. The composite with a low porosity possesses a low melting temperature and short duration of PCM melting process. The increase in ambient temperature causes the time required to trigger the melting of the carbon-foam/PCM composite to decrease but does not affect the melting duration. Conversely, an increase in heat flux reduces the melting duration.

Wear Prediction Method of Differential Planetary Roller Screws Considering the Ambient Temperature Variations

As a key component in fields such as high-precision machine tools, aerospace and weaponry, the thermal deformations in a differential planetary roller screw (DPRS) caused by the changes in ambient temperatures can lead to uneven load distribution and increased wear, which can seriously affect its transmission accuracy, efficiency, and service life. Therefore, the temperature rise of a DPRS at different ambient temperatures was studied using the block thermal network method, and the thermal deformations were calculated. A load distribution model of DPRS considering thermal deformation was developed, and a wear prediction method combined with surface roughness was proposed. The results show that the increase in ambient temperature has an obvious negative effect on the load distribution and wear depth of DPRS. Moreover, the DPRS temperature rise, load distribution and wear depth dramatically change with the variation of parameters such as load, speed and thread pitch. A DPRS durability test device that considers changes in ambient temperature was developed. Experiments with temperature rise and DPRS wear under different ambient temperatures were conducted to validate the theoretical analysis model.

Parametric Study on the Evaporation Characteristics of Biodiesel-Diesel-Methanol Microemulsion Droplets

ABSTRACT In order to investigate the evaporation characteristics of biodiesel-diesel-methanol microemulsions, an experimental method of droplet evaporation with post processing techniques is established. The droplet normalized square diameter (NSD), droplet temperature and images during evaporation process are used to analyze the evaporation characteristics at different ambient temperatures. The results indicate that the methanol volume percentage, initial volume of droplet and ambient temperature have evident influence on the evaporation characteristics of droplets. When the initial volume of droplet is 0.5 μL, BD95M5 (biodiesel-diesel blend (95%)+methanol (5%)) and BD85M15 (biodiesel-diesel blend (85%)+methanol (15%)) droplets do not show the puffing and micro-explosion phenomena during evaporation process, but BD75M25 (biodiesel-diesel blend (75%)+methanol (25%)) droplet exhibits micro-explosion evidently at ambient temperature of 573K. Puffing is observed for BD85M15 droplet, and micro-explosion is for BD75M25 droplet at ambient temperature of 773K. The droplet lifetime is decreased and the mean evaporation rate (MER) is increased with the increase of ambient temperature and methanol volume percentage in microemulsion. The evaporation process ends at 5.938 s/mm2, 5.417 s/mm2 and 4.792 s/mm2 for BD95M5, BD85M15 and BD75M25, respectively, and MERs of them are 0.087 mm3/s, 0.095 mm3/s and 0.108 mm3/s at ambient temperature of 573K. The MERs of BD95M5, BD85M15 and BD75M25 are 0.225 mm3/s, 0.244 mm3/s and 0.309 mm3/s, respectively, at ambient temperature of 773K. With the increase of initial volume of droplet, the occurrence of puffing and micro-explosion is strengthened. The MER of droplets with initial volume of 0.6 μL is the largest, which increases by 13.1% and 12.8% compared with 0.4 μL droplets and 0.5 μL droplets, respectively.

Performance analysis of a medium concentrated photovoltaic system thermally regulated by phase change material: Phase change material selection and comparative analysis for different climates

Thermal management of photovoltaic systems is important since their electrical output decreases with the increase in temperature. Thermal regulation of a photovoltaic system using a phase change material is an effective technique, but a careful selection of PCM in terms of its thermophysical properties is essential for its better performance. In this work, performance analysis of a novel medium concentrated photovoltaic system employing two mono-facial polycrystalline cells is carried out. The system is thermally regulated with a phase change material. An experimentally validated finite element-based coupled optical, thermal, and electrical model is used to analyze the system’s performance. The impact of the thermophysical properties of a PCM such as melting temperature, thermal conductivity, and heat of fusion on the thermal regulation of the system is studied using artificial neural networking methods. The optimum thermophysical properties of the PCM are determined using parametric analysis for the ambient temperatures ranging between 25 and 50 °C and a concentration ratio of 20×. Moreover, the performance of the system is analyzed using the optimum PCM for the semi-arid weather conditions of Lahore, Pakistan and the optimum PCM for oceanic weather conditions of Waterford, Ireland. It is found that the melting temperature, thermal conductivity, and heat of fusion of the PCM have a linearly indirect relationship with the temperature of the photovoltaic system while the ambient temperature has a linearly direct relationship with the photovoltaic system’s temperature. The melting temperature of a PCM should be 10–15 °C higher than the ambient temperatures up to the ambient temperature of 40 °C. The melting temperature of a PCM was found to be 5 – 10 °C higher than the ambient temperatures for ambient temperatures greater than 40 °C. The required thermal conductivity of a PCM increases with the increase in ambient temperature ranging from 10 to 12 Wm-1K−1 for the ambient temperature of 25 °C while 18–20 Wm-1K−1 for the ambient temperature of 50 °C. The suitable heat of fusion is found in the range of 210–220 kJkg−1. It is found that the optimum PCM for Lahore has melting temperature, thermal conductivity, and heat of fusion of 53–56 °C, 19 Wm-1K−1 and 220 kJkg−1 respectively. The optimum PCM for Waterford has melting temperature, thermal conductivity, and heat of fusion of 35–37 °C, 11 Wm-1K−1 and 220kJkg−1 respectively. The maximum temperature of concentrated photovoltaic cell for Lahore, Pakistan remains below 83 °C, while for Waterford, Ireland, it is below 59 °C for all the months in a year. From April to August, the output power is higher for Waterford with an average difference of 12%, while from September to March, Lahore has the higher power output with an average difference of 47%. The maximum power obtained for Lahore is 0.185kWh/day/m2, while for Ireland it is 0.213kWh/day/m2. A maximum deviation of 6% is found for electrical output and less than 3% for thermal output between simulated and experimental results during validation.

Effect of Annealing on PL Intensity of NaYF4:Er3+, Yb3+/Ca2+ Phosphor and the Application to Temperature Sensor

We have prepared NaYF4:Er3+/Yb3+/Ca2+ phosphors using the solvothermal method and discussed the influence of annealing on the crystal structure, morphology, and photoluminescence characteristics in this work. The results show that, with the increase of annealing temperature, the crystallization phase changes from a single cubic structure to a mixed phase of cubic and hexagonal phases and the morphology is also condensed from spherical particles to sheets. In particular, the PL intensity of the annealed phosphor becomes much stronger than that of the unannealed phosphor. An annealed NaYF4:Yb3+, Er3+/Ca2+ phosphor is selected as an example to investigate the performance of high temperature sensor based on the fluorescence intensity ratio between two green emissions. The measurement range and the maximum absolute sensitivity SA of the annealed sensor material are superior to the corresponding parameters of the same phosphor without annealing. The curve of relative sensitivity curve SR decreases as the ambient temperature increases, but that of the revolution δT presents an opposite trend. All the results show that the NaYF4:Er3+/Yb3+/Ca2+ phosphor is more suitable for application on the high temperature sensor after annealing.

The properties of sustainable aviation fuel I: Spray characteristics

This study measures the spray penetration, spray angle and spray volume of sustainable aviation fuel (SAF) experimentally using an optical constant volume combustion chamber under different ambient temperatures, injection pressures, and ambient pressures. The results show that when the ambient temperature increases from 200 °C to 300 °C, the spray penetration decreases by ∽10%–20%, while it further decreases by ∽40%–50% when the temperature increases from 300 °C to 400 °C. Furthermore, the spray penetration of SAF will reach its stable stage fastest at 400 °C. As the ambient temperature increases, the spray angle and spray volume of SAF decreased by 10%–20% and 50%, respectively. In addition, the spray penetration and spray volume of SAF increased by 10% and 20%, respectively, with an increase in injection pressure at 200 °C. An increase in injection pressure at 400 °C causes the decrease in spray penetration and spray volume of SAF by 20%, and both of them showed increasing and decreasing trends at the stable stage. Thus, increase in injection pressure has little effect on the spray angle. Moreover, the spray penetration and spray volume of SAF showed a decreasing trend on increasing ambient pressure, but significant effect was observed at a high temperature of 400 °C than at a low temperature of 200 °C. Conversely, the spray angle of SAF showed an increasing trend with an increase in ambient pressure, but this influence was larger at a low temperature of 200 °C than that at a high temperature of 400 °C.

Evolution characteristics of ethyl ether spray explosion process in 20L near-spherical vessel

As a biofuel with a wide range of uses, ethyl ether leakage may cause serious spray explosion accidents during storage and transportation, however, the evolution characteristics and process mechanism of ethyl ether spray explosion have not been thoroughly studied. Therefore, the effects of material temperature and ambient temperature on ethyl ether spray explosion at different concentrations are studied by means of spray explosion experiment system. In this paper, the development of ethyl ether spray explosion with a mass concentration range of 107.1–392.7 g/m3 was studied at different ambient temperature and material temperature. Where the ambient temperature range is 298.15–323.15 K, and the material temperature range is 298.15–323.15 K. Moreover, in this paper, the risk of spray explosion is more clearly understood through the classification of deflagration index, and the explosion characteristics of spray explosion are analyzed comprehensively according to the boiling point as the dividing line. The maximum explosion pressure and its arrival time, the rate of rise of the maximum explosion pressure and its arrival time are used as the basis to evaluate the effect of the explosion process of ethyl ether spray. The results show that when the ambient temperature is lower than the boiling point temperature of ethyl ether, the increase of ambient temperature has little effect on the explosion characteristics of ethyl ether spray. When the ambient temperature is higher than 308.15 K, the maximum explosion pressure and maximum rate of pressure rise of ethyl ether spray explosion increase. At medium and low concentrations(107.1 g/m3, 178.5–249.9 g/m3), the increase of ambient temperature is conducive to the rapid development of spray explosion, and the arrival time of maximum explosion pressure and pressure rise rate both show a decreasing trend. However, under the influence of incomplete combustion at high concentration, the explosion development rate is reduced. At lower material temperature, the maximum explosion pressure and the maximum rate of pressure rise increase with the increase of material temperature. When the material temperature is higher than 303.15 K, the ethyl ether droplet temperature is higher than the ambient temperature, and the heat loss of the droplet has a certain inhibition effect on spray explosion. Especially when the material temperature is high, the inhibition effect is more significant, so when the material temperature rises to 323.15 K, the maximum rate of pressure rise decreases. The effect of ambient temperature on the explosion grade is more obvious than that of the material temperature, and the effect on the explosion characteristics of ethyl ether spray is also greater.

Study on the Effects and Mechanism of Temperature and AO Flux Density in the AO Interaction with Upilex-S Using the ReaxFF Method

Atomic oxygen (AO), which is one of the most predominant and conspicuous space environmental factors in the low earth orbit, leads to severe deterioration of polymeric materials in spacecraft. The AO flux density and ambient temperature vary while a craft orbits in space; thus, it is necessary to pay close attention to the flux density and temperature effects on the mechanism of the AO interaction with materials. In past years, polyimide has been widely used on spacecraft due to its excellent performance—that is the reason why we chose Upilex-S as the object for study. It was analyzed using the ReaxFF reactive force field molecular dynamics simulation, respectively from the aspect of impact-induced temperature variation, mass loss, reaction product and erosion yield. The results show that dense AO deposition on the surface impedes further erosion at low temperatures, and the AO interaction with Upilex-S is exacerbated as the ambient temperature increases. However, the accelerating rate is inversely proportional to the ambient temperature, which means the higher the ambient temperature is, the slower it increases. On the other hand, the interaction rate of AO induced to Upilex-S is aggravated as the flux density increases at the lower stage, while the interaction rate begins to drop as the flux density increases at the higher level. The AO erosion effect is a complicated process rather than a simple summation of single atomic oxygen interactions. Our study could be used as a technical reference for the wide usage of Upilex-S on spacecraft.

Temperature induced wear mechanism transition of Ni-Co-W alloy coatings

A temperature induced wear mechanism transition of electrodeposited Ni-Co-W alloy coatings has been revealed. At room temperature, the wear rate of the coating exhibits little variation with sliding velocity or normal load. From 100 °C to 300 °C, the wear resistance of the coating is enhanced at high sliding velocity or high normal load. With increase of ambient temperature, the wear mechanism turns from typical abrasive wear with significant parallel grooves and wear debris on the worn tracks to mild oxidative wear with shallow grooves and adhered oxide layer on the worn surfaces. The improved wear resistance at high temperature can be ascribed to the transition of wear mechanism and the formation of uniform oxides layer covered on the worn surface.

Low-temperature joining of alumina ceramic and nickel by Al-Ni self-propagating nanofoil

To meet the requirements of alumina ceramics in delicate electronics, there is an urgent need for a low-temperature bonding technology that can realize a good combination of alumina and metal. In this work, alumina ceramics and nickel metals were successfully connected at a low temperature (25–150 °C) by Al-Ni self-propagating nanofoil as a heat source. The interface microstructure and element distributions of the solder joints from cross-section and fracture surface were investigated. In addition, the solder joint formation process was simulated by finite element analysis and molecular dynamics. These results showed that their shear strengths could be continuously improved with the growing temperature, which were 17.4 MPa (room temperature, 25 °C), 19.5 MPa (50 °C), 22.9 MPa (100 °C) and 25.69 MPa (150 °C). The Al2O3/Al-Ni nanofoil/Ni solder joints were prone to crack at the corner and boundary at Al2O3/solder interfaces due to the stress concentration. Moreover, the increase in ambient temperature not only raises the melting time and transient temperature during the self-propagating reaction, but also improves the interdiffusion of Ni and Sn atoms at the Ni/Sn interfaces.

Thermodynamic and feasibility analysis of using diesel generator exhaust gases for ship main engine preheating at port periods

In this study, the feasibility and potential impact on fuel consumption of the proposed preheating system driven by diesel generator exhaust gas instead of steam to satisfy main engine pre-heating demands especially under port operation conditions have been analyzed according to the 1st and 2nd laws of thermodynamics. The proposed novel term named performance criteria (PC) and exergy efficiency (ε) values of the main engine preheating and cooling water systems of the Ro-Ro ship selected for the case study under the existing voyage and port operating conditions have been determined by written Matlab-2021a codes merging CoolProp-6.4.2 database with Python. It was determined that even at the lowest operating load of the diesel generator (25%), the exhaust heat energy would be sufficient to preheat the main engine with also reducing the fuel consumption. As a result, during the 12-hour port period, 22% of the boiler fuel consumption and 8% of the ship's fuel consumption can be saved. Accordingly, if a shipping company uses Mine Gas Oil as fuel, it will be able to achieve fuel savings of approximately US$ 32.000 on annual basis. Considering the fuel saving values, it has been determined that 1.016 tons of CO2 emissions for per port operation and 106 tons of annual CO2 emissions can be reduced. It was determined that, the PC and Ɛ values of the system decrease as the ambient temperature increases. In this context, there is a 7% decrease in the PC and a 5% decrease in the Ɛ for existing system and 8% decrease in the PC and a 2.5% decrease in the Ɛ for proposed system. It was also determined that the proposed new system is both physically and economically feasible and that the investment cost, which was determined to be in the range of US$ 30.000-US$ 35.000, can pay for itself after 1 year.

Short-term mediating effects of PM2.5 on climate-associated COPD severity

The impact of short-term exposure to environmental factors such as temperature, relative humidity (RH), and fine particulate matter (PM2.5) on chronic obstructive pulmonary disease (COPD) remains unclear. The objective of this study is to investigate PM2.5 as a mediator in the relationship between short-term variations in RH and temperature and COPD severity. A cross-sectional study was conducted on 930 COPD patients in Taiwan from 2017 to 2022. Lung function, COPD Assessment Test (CAT) score, and modified Medical Research Council (mMRC) dyspnea scale were assessed. The mean and differences in 1-day, 7-day, and 30-day individual-level exposure to ambient RH, temperature, and PM2.5 were estimated. The associations between these factors and clinical outcomes were analyzed using linear regression models and generalized additive mixed models, adjusting for age, sex, smoking, and body mass index. In the total season, increases in RH difference were associated with increases in forced expiratory volume in 1 s (FEV1) / forced vital capacity (FVC), while increases in temperature difference were associated with decreases in FEV1 and FEV1/FVC. Increases in PM2.5 mean were associated with declines in FEV1. In the cold season, increases in temperature mean were associated with decreases in CAT and mMRC scores, while increases in PM2.5 mean were associated with declines in FEV1, FVC, and FEV1/FVC. In the warm season, increases in temperature difference were associated with decreases in FEV1 and FEV1/FVC, while increases in RH difference and PM2.5 mean were associated with decreases in CAT score. PM2.5 fully mediated the associations of temperature mean with FEV1/FVC in the cold season. In conclusion, PM2.5 mediates the effects of temperature and RH on clinical outcomes. Monitoring patients during low RH, extreme temperature, and high PM2.5 levels is crucial.Capsule of findingsThe significance of this study is that an increase in ambient RH and temperature, as well as PM2.5 exposure, were significantly associated with changes in lung function, and clinical symptoms in these patients. The novelty of this study is that PM2.5 plays a mediating role in the association of RH and temperature with COPD clinical outcomes in the short term.

Thermal comfort of personal protective equipment (PPE) wearers in different temperatures and activity conditions

To avoid virus infections, healthcare workers have to wear personal protective equipment (PPE) during work. However, the high temperature and humidity in PPE threaten their physical and mental health. In this study, thermal physiological and psychosocial responses of PPE wearers at different temperatures (26 °C, 30 °C) and different combinations of alternating activity intensities (transcribing/sitting, walking/standing) were observed by experiments. The results show the increase in ambient temperature has a greater influence than the activity intensity on the increase in average skin temperature, whereas the opposite is true for heart rate and tympanic temperature. The thermal physiological state of the participants is mostly affected under ThAh condition. The average weight change can reach 586.8 g, and the participants' heart rate, average skin temperature, and tympanic temperature can reach 133bpm, 36 °C, 37.8 °C, respectively. Due to significant heat accumulation, the average heart rate during 100–120 min (standing), exceeding 120 bpm, was even higher than that during 40–60 min (walking) and the tolerance time for thermal discomfort for PPE wearers may not exceed 100 min under ThAh condition. And the discomfort caused by wearing masks and high humidity are the two most frequently reported occurrences. Furthermore, forehead, chest, and back are suggested to be primarily considered for maximum effectiveness if designing improvement measures to optimize thermal comfort for PPE wearers. This study adopted an experimental condition design that alternated between different activity intensities to reflect the working states of healthcare workers, providing a better understanding of the thermal physiological state of healthcare workers wearing PPE and could serve as a reference for future research in developing PPE cooling strategies.