•SI-traceability of relative humidity extended to very high dew-point temperatures.•Degree of equivalence of three national humidity measurement standards.•Demonstrated relative humidity calibrations ...at very high dew-point temperatures.
Three European National Metrology Institutes (NMIs), VSL, LNE-CETIAT and INRiM, extended their relative humidity calibration capabilities to temperatures up to 170 °C, dew-point temperatures up to 150 °C and pressures up to 600 kPa. In order to test the equivalence of the respective calibration set-ups, 4 commercial high-temperature relative humidity sensors were exchanged among the three NMIs and calibrated at different combinations of relative humidity (19 %rh to 70 %rh), air temperature (100 °C to 170 °C) and pressure (100 kPa to 500 kPa), realizing dew-point temperatures of either 81.5 °C or 127 °C. The initial and final measurements at VSL showed that the stability of the selected sensors was sufficient for comparing the different calibration set-ups. The results of the comparison showed that VSL and LNE-CETIAT facilities agreed within their claimed uncertainties (≤0.3 %rh), while discrepancies of up to 4 %rh were observed between VSL and INRiM facilities.
δ18O in speleothem carbonates is a common archive for paleoclimate on land. Recently, it has been shown that triple oxygen isotopes in CaCO3 (given as ...Oexcess17=106ln(10−3δ17O+1)−0.528(ln(10−3δ18O+1)) record Oexcess17 of its parent water, thus providing additional paleo-hydrology information, primarily about relative humidity. The O17 fractionation between CaCO3 and water has been determined in biogenic and synthetic carbonates. In speleothems, however, this fractionation is expected to be modified by kinetic isotope effects associated with CO2 degassing from cave drip water. Here, we used Soreq Cave as a case study to examine this fractionation and the use of Oexcess17 in speleothems as an archive for paleo rainfall composition. We first characterized Oexcess17 in rainfall collected above the cave. The Oexcess17 value in amount weighted integrated rainfall was 49 per meg, consistent with the low relative humidity at the moisture source of the Eastern Mediterranean Sea. The measured cave water was slightly lower in Oexcess17 and higher in δ18O relative to rainfall, due to modifications of the infiltrating water by epikarst processes such as evaporation and mixing. Oexcess17 in CO2 extracted from CaCO3 of modern speleothems was compared to that in modern cave water, to calculate the carbonate-water fractionation slope (θ=ln17α/ln18α). The resulting θ in Soreq Cave was 0.5230±0.0002, consistent with that observed in other carbonates, indicating the lack of significant dis-equilibrium effects in speleothems Oexcess17. Hence, the common fractionation slope can be used together with a speleothem-specific α18 to reconstruct rainfall Oexcess17 from speleothem carbonates. Whereas speleothems from a variety of caves can be used through this approach to reconstruct Oexcess17 in paleo rainfall, the atmospheric processes that govern rainfall Oexcess17 are expected to be region-specific. Oexcess17 measurements in ancient Soreq speleothems are expected to reveal potential glacial-interglacial changes in moisture source conditions as well as possible changes in epikarst processes over time.
•We examine Oexcess17 in Soreq Cave speleothems, cave water, and rainfall.•Rainfall Oexcess17 of 49 per meg reflects the low RH over the Mediterranean.•Speleothem-water fractionation slope is similar to that in other carbonates.•Kinetic effects in stalagmite formation do not significantly affect Oexcess17.•Speleothems can be used as an archive for rainfall Oexcess17 and moisture sources.
A real-time humidity sensor based on a microwave resonator coupled with a poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) conducting polymer (CP) film is proposed in this paper. ...The resonator is patterned on a printed circuit board and is excited by electromagnetic field coupling. To enhance the sensitivity of the sensor, the CP film is located in the area with the strongest electric field in the resonator. To investigate the performance, the proposed sensor is placed alongside a reference sensor in a humidity chamber, and humidity is injected at room temperature. The experimental results indicate that the electrical properties of the resonator with the CP film, such as the transmission coefficient (S
) and resonance frequency, change with the relative humidity (RH). Specifically, as the RH changes from 5% to 80%, S
and the resonance frequency change simultaneously. Moreover, the proposed sensor exhibits great repeatability in the middle of the sensing range, which is from 40% to 60% RH. Consequently, our resonator coupled with the CP film can be used as a real-time humidity-sensing device in the microwave range, where various radio-frequency devices are in use.
The coronavirus disease 2019 (COVID-19) pandemic is the defining global health crisis of our time and the greatest challenge facing the world. Meteorological parameters are reportedly crucial factors ...affecting respiratory infectious disease epidemics; however, the effect of meteorological parameters on COVID-19 remains controversial. This study investigated the effects of temperature and relative humidity on daily new cases and daily new deaths of COVID-19, which has useful implications for policymakers and the public. Daily data on meteorological conditions, new cases and new deaths of COVID-19 were collected for 166 countries (excluding China) as of March 27, 2020. Log-linear generalized additive model was used to analyze the effects of temperature and relative humidity on daily new cases and daily new deaths of COVID-19, with potential confounders controlled for, including wind speed, median age of the national population, Global Health Security Index, Human Development Index and population density. Our findings revealed that temperature and relative humidity were both negatively related to daily new cases and deaths. A 1 °C increase in temperature was associated with a 3.08% (95% CI: 1.53%, 4.63%) reduction in daily new cases and a 1.19% (95% CI: 0.44%, 1.95%) reduction in daily new deaths, whereas a 1% increase in relative humidity was associated with a 0.85% (95% CI: 0.51%, 1.19%) reduction in daily new cases and a 0.51% (95% CI: 0.34%, 0.67%) reduction in daily new deaths. The results remained robust when different lag structures and the sensitivity analysis were used. These findings provide preliminary evidence that the COVID-19 pandemic may be partially suppressed with temperature and humidity increases. However, active measures must be taken to control the source of infection, block transmission and prevent further spread of COVID-19.
Display omitted
•First study to explore the effects of temperature and humidity on the daily new cases and deaths of COVID-19 worldwide.•We used log-linear GAM to analyze the effects.•We considered the lag effects and the cumulative effects of weather conditions.•Temperature and relative humidity were both negatively related to the daily new cases and daily new deaths of COVID-19
In this study, it was aimed to reveal the energy and exergy losses caused by air temperature and water vapor in the air, which are the most important elements of climatic conditions, in ...heating-cooling processes and in the operation of the heat pump system. Two water source heat pumps were used in the system established for the experimental analysis. The relative humidity and temperature of the atmospheric air were reduced with the first heat pump. Relative humidity levels of 30%, 40%, 50%, 60%, 70%, 80%, 90%, respectively, were provided to the air brought to 20 °C, 23 °C, 26 °C, 29 °C, 32 °C temperature levels in the system. The effects of the air reaching the desired humidity and temperature on the 2nd heat pump were determined with temperature, humidity, pressure, flow and ampermeters for air, water and refrigerant. The results were subjected to thermodynamic calculations and presented graphically. This experimental studies done revealed that water vapor (relative humidity) in the air increases the exergy destruction on heating and cooling works. It was revealed that the heat pump components, especially the evaporator, suffer high exergy losses. With the increase of relative humidity, exergy and energy losses in heat pumps and each of their components also increase. In this study, it was revealed that the heating and cooling works became more difficult with the increase of water vapor in the air. Accordingly, it was observed that the heat pump system elements can be operated in different styles and capacities in high humidity areas.
•With the increase in temperature, the exergy loss in the system components increases.•The exergy loss in the condenser decreases with increasing relative humidity.•The highest exergy destruction occurs in the evaporator component.
The degree of reaction and the reaction kinetics of the reactants in geopolymers correlate closely to their mechanical properties and their durability. However, quantifying the reaction using ...conventional methods is challenging, especially for alkali activated siliceous fly ash with low reactivity.
In the present study, a novel method to estimate the reaction kinetics of geopolymers at early ages based on the evolution of the internal relative humidity is proposed. The experimental results show increasing internal relative humidity of the two studied fly-ash based geopolymers with increasing hydration time. The internal relative humidity increases due to the reduction of the ion concentration in the pore solution as they become consumed during the reaction of the fly ash. Verified by comparison with compressive strength, heat release in isothermal calorimetry and degree of reaction measured with selective dissolution, this new method is useful to estimate the reaction kinetics of geopolymers having limited self-desiccation.
PDF
