Stable Relative Humidity Research Articles

Sensitivity of Philippine historically damaging tropical cyclone events to surface and atmospheric temperature forcings

As the climate warms, sea surface temperature (SST) is projected to increase, along with atmospheric variables which may have an impact on tropical cyclone (TC) properties. Climate models have well-known errors in simulating current climate SSTs that will likely affect future TC projections. Therefore, a better understanding of the impact of SST changes will help us identify the largest uncertainty in projecting TC changes. This study employs three different and independent methodologies to investigate the impact of sea surface and atmospheric temperature changes and tropical cyclone (TC) characteristics, focusing on three historically damaging TCs in the Philippines: Typhoons Haiyan, Bopha, and Mangkhut. These methodologies include initially simulations with uniform SST anomalies between −4 to +4°C, then experiments using delta from CMIP6 CESM2 for SST and atmospheric temperature in the far future, and, finally, simulations imposing Radiative-Convective Equilibrium (RCE) conditions. The experiments reveal significant insights into TC dynamics under varying environmental conditions. Changes in SSTs resulted in changes in TC track, intensity, and rainfall. In the positive SST simulations, TCs tended to move northwards and resulted in substantial increases in maximum wind speeds reaching a difference of up to 10, 13, 23 ms−1 for Typhoons Haiyan, Bopha, and Mangkhut, respectively. Analysis of the accumulated rainfall also showed that increased SST results in increased rainfall. Inclusion of atmospheric warming offsets the intensification due to SST change. Moreover, warmer SSTs resulted in slower-moving TCs and increased TC size. Further analyses incorporating atmospheric temperature adjustments derived from CESM2 and RCE simulations offer better insights on TC response. Under near-RCE conditions, TCs exhibit reduced sensitivity to SST changes, with smaller intensity and size modifications simulated when stable relative humidity is imposed. The smaller changes in TC intensity and size observed in these experiments suggest that maintaining atmospheric stability through pre-storm atmospheric adjustments dampens the response of TCs to SST warming.

Evolution behavior of adhesion force with continually changed relative humidity revealed on AFM

ABSTRACT Adhesion forces on various surfaces with different hydrophilicity were measured by atomic force microscopy in the force-volume mode and at a location to study the relative humidity (RH) dependence. With an increasing-stable-decreasing trend in RH, the force in the force-volume mode usually exhibits a constant-increase-constant-decrease-constant variation. Surfaces with partial or complete hydrophobicity exhibited a much larger increase compared to a hydrophilic one. However, the behavior on some surfaces was distorted due to a decrease at high stable RHs. Contrastively, the behavior at a location could also display the same behavior. Both gradual and sudden changes were observed at a single location as RH changed. At high stable RHs, the force displayed complex behaviors, indicating unique characteristics at each location. Therefore, the measurement at a location is not suitable to study the RH dependence. Specially, the force measured on silica in the force-volume mode has the mentioned behavior. However, the force at a location can remain stable, gradually/sharply increase or decrease, and suddenly jump or drop with RH. These observations are attributed to the evolution of a water bridge, which is largely influenced by thin-film flow. The findings provide deeper insights into adhesion mechanisms at different RHs.

Impact Analysis of Super Typhoon 2114 ‘Chanthu’ on the Air Quality of Coastal Cities in Southeast China Based on Multi-Source Measurements

The northward typhoon configuration along the southeast coast of China (TCN-SEC) is one of the key circulation patterns influencing the coastal cities in southeast China (CCSE). Here, we analyzed the air quality in CCSE during the high-incidence typhoon period from 2019 to 2021. Multi-source measurements were carried out to explore the impact of super typhoon 2114 ‘Chanthu’ on the air quality in CCSE. The results showed that the TCN-SEC and its surrounding weather situation had a favorable impact on the increase in pollutant concentration in CCSE, especially on the increase in O3 concentration. From 13 September to 17 September 2021, affected by the cyclonic shear in the south of super typhoon 2114 ‘Chanthu,’ the strong wind near the ground, stable relative humidity, strong precipitation, and the significantly reduced wind speed had a substantial effect on PM10, PM2.5, SO2, and NO2 concentrations. Calm and light air near the ground, weak precipitation, high daily maximum temperatures, and minimum relative humidity may provide favorable meteorological conditions for the accumulation of O3 precursors and photochemical reactions during the day, resulting in the daily peak values of O3 exceeding 160 μg/m3. The evolution of wind, relative humidity, and boundary layer height could play an important role in the variations in PM10 and PM2.5 concentrations by influencing pollutant accumulation or diffusion. It was suggested that the atmospheric structure of horizontal stability and vertical mixing below 1500 m could play a significant role in the accumulation and vertical distribution of ozone. The results highlight the important role of typhoons in the regional environment and provide a scientific basis for further application of multi-source observation data, as well as air pollution control.

Sustainable cooling strategies to minimize water consumption in a greenhouse in a hot arid region

Evaporative cooling systems are the currently used technology for providing cooling to greenhouses in arid regions where typically the greenhouse is ventilated. However, they consume a large quantity of water to cool the air. A closed greenhouse is proposed that uses earth-air heat exchangers (EAHE) and fogging to control the interior temperature and relative humidity in a water-efficient manner. A numerical model has been developed for the greenhouse and EAHE, and have been validated against experimental data collected from literature. Simulations are performed to compare the proposed closed greenhouse performance against the fan-pad system in a ventilated greenhouse in maintaining a suitable temperature and humidity, and to estimate the water usages. The EAHE reduced the water consumed by the fogging system by 50 % and the maximum interior temperature from 50 °C to 35 °C. The temperature reduction was found comparable to a fan-pad system with a ventilation rate of 20 air changes per hour, however, with a more stable relative humidity at approximately 75 %. Furthermore, water used for cooling was lower by one tenth of that of the fan-pad system, reducing it from 53 litre/day to 5 litre/day.

Hygrothermal conditions for the biological aging of sherry wine

The present work analyzed the hygrothermal environment of several prestigious warehouses where sherry wines of “Fino” and “Manzanilla” type are made. Through descriptive statistics, frequency histograms and psychrometric diagrams of temperature and relative humidity variations have been obtained. In addition, other factors such as the stability and uniformity of the interior environment have been quantified. The results showed significant temperature variations throughout the year (limit values of 5 °C and 31 °C), with a more stable relative humidity (between 60% and 90% for most of the year). Indoor conditions varied much more rapidly than in wineries for the aging of red wine, as a result of constant ventilation. Therefore, the annual average stability was 2.0 ± 0.8 °C per day and 0.14 ± 0.12 °C per hour. Vertical uniformity decreased in spring and summer, with stratification values close to 0.5 °C/m and 3% r.h./m. The monitored indoor environment is outside the comfort ranges described in the literature for extended periods of time (in the most extreme case, 96% of the time outside the recommended interval). For that reason, a reference psychrometric comfort diagram was proposed. Industrial relevanceFor the first time, the hygrothermal behavior of several wineries producing high quality wines (very high scores in the oenological guides) was extensively analyzed. The results of the study, which include monthly comfort intervals, should be a very useful tool for the sherry wine industry, in order to control and ensure optimal development of the flor yeast film. It should also be taken into account for the correct design of new wineries or the rehabilitation of abandoned warehouses.

First biological data, associated fauna, and microclimate preferences of the enigmatic cave-dwelling beetle Dalyat mirabilis Mateu, 2002 (Coleoptera, Carabidae)

Dalyat mirabilisis an extraordinary troglobite carabid described in 2002 from the cave Simarrón II in the southeast of the Iberian Peninsula (Spain). A new subfamily Dalyatinae was erected to accommodate this species with remarkable morphological characters and adaptations to live underground. In addition to the former original descriptions, there is only one more study and it aimed to elucidate its evolutionary history. Its closest living relative belongs to the genusPromecognathusin North America and both groups seem to have diverged sometime in the late Jurassic to early Cretaceous. In this work, the phenology ofD. mirabilis, its associated invertebrate fauna and the environmental conditions of the cave Simarrón II were studied for a full year cycle. This carabid is not evenly distributed in the cave, in time or space. It is most abundant during the winter months, wet season, and it disappears from the top layer of the substrate in the summer. A positive correlation was found between the number of carabids captured per trap and the distance to the entrance of the cave; most specimens were captured in traps farthest from the entrance and located in the chamber known as Vias Salas Negras. Furthermore, several spatially-resolved analyses integrating relative humidity, temperature, and the number of captures per trap showed thatD. mirabilisprefers Vias Salas Negras for having a higher and more stable relative humidity than other chambers in the cave. Larvae were never captured, regardless of intense efforts to collect them for years. Finally, 30 other invertebrate species belonging to 12 different Orders were captured in the cave and are listed here, 25.8% are troglobites, 29.0% troglophiles and 45.2% troglexenes. The data from this study was used for an initiative to protect this cave and its remarkable fauna. Some of the measures taken by the Administration include the control of human visits to the cave, the installation of a perimetral fence surrounding the entrance, and the installation of an informative panel at the exterior of the cave describing the endemic entomological fauna it contains.

Embedded Optical Fibre with Fibre Bragg Grating Influence on Additive Manufactured Polymeric Structure Durability.

Additive manufacturing (AM) polymers are applied in many branches of the industry due to the possibility of fast and accurate production of elements with various and complex shapes. Fibre Bragg grating sensors (FBG) are widely applied in structural health monitoring (SHM) systems. The main objective of this research is to perform analyses of the influence of embedded FBG sensors on AM polymer elements’ durability. Two polymers (M3 X and M3 Crystal) with different mechanical properties were analysed. The tests were performed on samples with FBG sensors embedded in (different alignment) and attached to the surfaces of the elements. Firstly, the samples were exposed to elevated or sub-zero temperatures under stable relative humidity levels. The strain in the samples was measured using fibre Bragg grating (FBG) sensors. The achieved results allow us to determine the relationships between strain and temperature for both materials and the differences in their mechanical response to the thermal loading. Then, the samples were subjected to a tensile test. A comparison of the tensile strength values was performed for the samples without and with embedded FBG sensors. The samples after the tensile tests were compared, showing differences in the mechanisms of failures related to the polymers and the thermal treatment influence on the material internal structure. Additionally, strain values measured by the FBG sensors were compared to the strain values achieved from the testing machine showing a good agreement (especially for M3 X) and indicating the differences in the materials’ mechanical properties. The achieved results allow us to conclude there is a lack of influence of embedded FBG sensors on the mechanical durability of AM polymers.

Effect of Environmental Humidity on the Acoustic Vibration Characteristics of Bamboo

Bamboo musical instruments, such as bamboo flute and Ching-hu (Beijing opera fiddle), can generate a crisp and melodious sound closely related to the delicate multiscale pore structure of bamboo. Bamboo is a natural hydrophilic material, and its acoustic vibration characteristics are highly sensitive to changeable environmental humidity levels. Herein, we investigated the acoustic vibration characteristics of bamboo under three conditions: constant relative humidity (status I), changeable relative humidity (status II), and subjected to water extraction (status III). Three typical parameters were selected as evaluation indicators of bamboo acoustic vibration characteristics, namely, specific dynamic elastic modulus (E′/ρ), loss tangent (tanδ), and acoustical converting efficiency (ACE). The outer bamboos (OB) had higher E′/ρ and ACE but lower equilibrium moisture content (EMC) and tanδ than the inner bamboos (IB). Under status I, bamboo showed the maximum E′/ρ and ACE and the minimum tanδ at 35% RH (relative humidity) and about 6% MC. Compared with the bamboo under status II, the bamboo under status I retained higher E′/ρ and ACE and lower tanδ. However, the bamboo under status (III) reached the maximum E′/ρ and ACE and the minimum tanδ. The bamboo musical instrument is made of bamboo with proper removal of water-soluble extractives and high fiber volume fraction and stored in a stable relative humidity environment of 35%, which has suitable acoustic vibration characteristics.

Ten questions concerning the potential of digital production and new technologies for contemporary earthen constructions

Earth is one of the oldest and till now intensively used natural building material. Around 30% of the world population still lives or works in buildings constructed out of earth. Most of them dwell in simple huts of rural communities or traditionally hand-crafted buildings. However, a growing number of people looking for healthy, environmentally friendly buildings in so called developed societies experience benefits of earthen construction materials. Due to the hygrothermal potential of clay, these benefits of earthen constructions include evaporative cooling during cooling periods and stable relative humidity levels indoors during the heating season. In addition, earthen building materials may contribute to the urgently needed circular economy, as earthen constructions like earth blocks or earth dry boards are reusable and earth plasters and mortars are replasticisable through the addition of water, as long as no chemical binder is added. Research gaps regarding physical properties, missing standardisation concerning building law and modern construction methods, and a limited number of manufacturers are hindering a wide application of earthen construction worldwide. Meanwhile, new digital production techniques evolve, which may elicit the potential of earth as future building material. Therefore, this Ten Questions article presents the state-of-the art and research gaps related to earth as building material in light of the potential of new digital production techniques like robotic fabrication or additive manufacturing. Such discussion includes new opportunities to combine the natural performance of the material with future-oriented construction systems and a new growing circular economy.

Underlying mechanism of diurnal change in thermal sensation response at high relative humidity.

Diurnal changes in physiological and behavioral responses to constant relative humidity (RH) were investigated in summer to validate a hypothesis that thermal sensation responses (TSR) vary with the diurnal cycle while maintained at stable RH's of 60, 70, or 80%. Seven lightly clothed male subjects were exposed to one of three RH while air temperature (Ta) was held at 28°C from 9:00-18:30. Mean skin temperature (T‾sk) and tympanic temperature (Tty) were monitored at 2-min intervals throughout the experimental period. Cutaneous warm and cool sensation thresholds and stratum corneum water content (SCWC) on the anterior forearm, posterior forearm, and anterior thigh, finger blood flow rate (SkBF) were measured by a thermal stimulator controlled by a Peltier element (Intercross-230; Intercross, Co., Tokyo, Japan), a water content of stratum corneum monitor (Corneometer CM825 & MPA 5; Integral Co., Tokyo, Japan), and a laser flowmeter (ALF21; Advance Co., Tokyo, Japan), accordingly at the end of three periods: 9:30-10:30, 13:30-14:30, and 17:30-18:30. The TSR and the thermal comfort response were also recorded using subjective scales of thermal sensation and comfort thresholds at the end of three periods. The Tty and mean skin temperature (T‾sk) remained unchanged during the day under all RH conditions. Temperature difference between warm and cold sensation thresholds and SkBF decreased slightly towards the evening under all RH conditions whereas SCWC increased from the morning to the evening at 60% and 80% RH. Behaviorally, the subjects responded more than "slightly warm" at 70%, and 80% RH, and then the TSR changed significantly (p<0.05) to less than "slightly warm" in the evening, although T̅sk remained unchanged at 34.0°C. The results from the previous study in winter was reconfirmed, and the data verify the hypothesis that TSR changes diurnally even though subjects are exposed to a constant and high RH's and stable Ta. It was confirmed in summertime as previously shown in wintertime that the combined reduction in SkBF to increases SCWC when exposed to high RH explains the altered TSR although Ta are unchanged.

Vertically increased NO3 radical in the nocturnal boundary layer

In the nocturnal boundary layer, nitrate radical (NO3) has an important contribution to atmospheric chemistry through oxidation of nitrogen oxides and hydrocarbons. Vertical distributions of NO2, O3 and NO3 were measured by four differential optical absorption spectroscopy instruments at meteorological tower in Beijing from June 1 to July 22, 2019. The results show the mean diurnal variations of NO2, O3, and NO3 display a single peak (up to 65.0 ppbv, 196.8 ppbv and 317.5 pptv, respectively) in time. O3 and NO3 mixing ratios generally increased against heights, which is opposite to NO2, suggesting the contribution of O3 to NO3 production at higher altitude. According to the correlation coefficients between NO3 production rates (PNO3) and NO2 or O3 levels, PNO3 was sensitive to NO2 mixing ratio at higher altitude but to O3 near the ground. Averaged NO3 lifetimes (τNO3) of lowest, middle, upper and highest layer intervals were 104, 118, 164 and 213 s, respectively, which indicates τNO3 increase against height and explains why NO3 mixing ratios are larger at higher altitude to some extent. Main control factors of NO3 removal changed from gas-phase reactions to N2O5 hydrolysis with height increase. When relative humidity (RH) exceeded 70% or PM2.5 level exceeded 50 μg·m−3, τNO3 was almost less than 300 s with mixing ratio lower than 70 pptv. The clear negative dependence of τNO3 on RH and PM2.5 reveals the influencing factors on indirect loss. Under polluted conditions, vertical profiles of NO2, O3 and NO3 varied drastically. Stable atmosphere (low nocturnal boundary layer height and thermal inversion), RH level and RH gradient are the main reason for the evident difference in NO3 gradient. Vertically increased NO3 radicals may imply the formation of nitrate aerosols and further increase the nitrate content in high- altitude particulate matter.

Experimental and Numerical Analysis of a Novel Display Case Design: Case Study of the Renovated Anne Frank House

ABSTRACT Many museums are housed in historic buildings, sometimes the building itself is part of the museum collection. Creating a stable environment by providing a nearly constant temperature and relative humidity at correct levels decreases the risk of object degradation. Maintaining this steady indoor environment, however, increases energy consumption and risks to the historic building. Museum display cases offer a solution to the mitigation of risks to which valuable objects may be subjected by providing an extra layer of protection to indoor climate fluctuations. The Anne Frank House is a historic house museum located in Amsterdam. The museum has undergone several renovations in the last years to deal with an increase in the number of visitors to over 1.2 million a year. The original diaries and other documents of Anne Frank are permanently on display in the Anne Frank House. With the recent refurbishment the possibility arose to design a new state-of-the-art display case. This study presents the results of the experimental research related to the design, performed in-situ. The temperature and relative humidity in the new exhibition space and inside the new display cases were monitored to gain insight into the hygrothermal behavior of these controlled environments. A complementary numerical study was performed to investigate effects of dynamic climate control of the exhibition gallery and climate conditions in the display case under various circumstances. Four main conclusions are presented in this paper. The investigated display case design is able to provide a stable relative humidity environment by means of silica gel, while using an active box-in-box climate control system to create stable temperature conditions. The inner case temperature depends on the temperature supplied by the display case air handling unit. Protocols must be in place in case of malfunction or failure of the climate control system of the display case. The air handling unit of the case needs to be shut off to create a passive environment for the objects on display until necessary actions are taken. Exhibition gallery set points can be less stringent when susceptible museum objects are on display in the display case. The environments are separated and provide an opportunity for energy saving set point strategies. The last conclusion drawn is that the numerical study provides valuable insight into imposing dynamic control of set points for temperature and relative humidity in the exhibition gallery and the effect on the display case environment.

High time-resolution measurement of light scattering hygroscopic growth factor in Beijing: A novel method for high relative humidity conditions

The light scattering hygroscopic growth factor (f(RH)), which quantifies the hygroscopicity of polydisperse ambient aerosols at continuous relative humidity (RH) levels, is usually measured by a humidified nephelometer system. The hygroscopicity of aerosol will change evidently under high RH conditions (>90%). However, in previous studies, only the aerosol hygroscopicity below 90% RH was generally obtained and discussed due to the difficulty in creating a stable high RH and measuring it accurately. In view of these conditions, an improved high-resolution humidified nephelometer system was established to observe the f(RH) of PM2.5 for a wide RH range between 30 and 96% in an urban area of Beijing during three seasons (winter, summer, and autumn) in 2017. Two sensors were used to calculate the humidified RHs, which made the uncertainty in the f(RH) at a high RH much lower than that in previous studies (lower than 10% for the maximum value). It was found that the f(80%) at 525 nm of PM2.5 was evidently higher under polluted conditions and highly correlated with the fractions of all of the water-soluble ions. A two-parameter fitting equation was selected to fit the observed f(RH) data. The f(RH) data under polluted conditions were more uniform with higher fitting R2 values during the summer and autumn. The hygroscopicity of aerosols has probably increased compared with that in the previous study conducted in the NCP. The fitted curves of the seasonal f(RH) data showed a significant dependence on the wavelength and increased with increasing wavelength. The hygroscopicity of PM2.5 for RH > 90% was definitely lower than that for 80% < RH ≤ 90%. The hygroscopic growth of aerosols under high RH conditions can probably be overestimated by only using f(RH) data below a RH of 90%.

Fundamentals of the Local Anodic Oxidation of Graphene for Scalable Applications

Using a novel instrument previously reported by our group [1], we have been able to perform Local Anodic Oxidation (LAO) over monolayer graphene to create unprecedented large areas (larger than mm2) of single layer Graphene Oxide (GO) with any shape and in a very short time (a few minutes). Our instrument is equipped with three electromechanical steppers with 0.05 µm accuracy and 1 µm precision, and each stepper with a linear piezoactuator. It operates at speeds up to 15 mm/s, and includes a steel/Ni spring probe of typically 6 µm radius to work in tapping or contact mode. The equipment is provided with a humidity control system that allows maintaining a stable Relative Humidity (RH) environment, together with a system of supply and electrical monitoring. Thus, electrical signal coming from the tip-sample interaction is continuously monitored (by means of a high speed oscilloscope). When the tip approaches to graphene on a wet atmosphere (RH higher than 40%), it is commonly accepted that a water bridge is created between them. When a negative bias is applied to the tip respect to the grounded graphene (in our case we operate between 20V - 40 V), the LAO phenomena takes place [2] (Fig. 1a). The process firstly consists on electrical water ionization in H+ and OH- ions. Hydroxyl anions are then conducted to the graphene surface, which is thus oxidized. Within a specific RH range, the oxide patterns created show a good reproducibility and regular shape (Fig. 1b). Controlling the movement of the tip, we can draw the desired patterns over the graphene or any other 2D-substrate (Fig. 1c). We have extensively studied and optimized the influence of the experimental variables affecting the process, like applied bias, contact time or relative humidity. This LAO procedure is so a very powerful tool for the fabrication of electrical devices. Also, the possibility of chemical functionalization of GO allow us to design a large variety of utilities like (bio)chemical sensors, supported catalysts, etc. In addition, we have been able to record the electrochemical trace generated during the oxidation reaction of graphene. To our knowledge, it is the first time these records have been reported. Moreover, based on these data, we have formulated a theoretical model based just on classical first principles that predicts the behavior of the LAO process over graphene. This model shows a very accurate fit for the dependence of the oxide pattern expansion with the applied voltage (Fig. 2a), with the contact time (Fig. 2b), and also for the evolution of the recorded transient electric current (Fig. 2c). This model reveals very relevant information about the processes governing LAO. First, at the beginning (< 20 ms), most of the total current I(t) passing through the tip-substrate junction does not come from the electrochemical reaction but from residual conductance of the non-oxidized graphene. We call this component drift current, IT(t). Second, for longer times (>200 ms), the total current becomes dominated just by the electrochemical reaction, and the drift component almost vanishes. We call this component electrochemical current, IEC(t) (Fig. 2c). Third, the process is mainly driven by the electric field increase at the edge of the pattern. And fourth, the GO generated has a very high oxidation degree. This work opens new promising fields for development of extensive fabrication methods, technical applications and the study of anodic oxidation processes of conducting and any 2d material at large scales.

A field portable method for the semi-quantitative estimation of dehydration tolerance of photosynthetic tissues across distantly related land plants.

Desiccation tolerant (DT) plants withstand complete cellular dehydration, reaching relative water contents (RWC) below 30% in their photosynthetic tissues. Desiccation sensitive (DS) plants exhibit different degrees of dehydration tolerance (DHT), never surviving water loss >70%. To date, no procedure for the quantitative evaluation of DHT extent exists that is able to discriminate DS species with differing degrees of DHT from truly DT plants. We developed a simple, feasible and portable protocol to differentiate between DT and different degrees of DHT in the photosynthetic tissues of seed plants and between fast desiccation (< 24 h) tolerant (FDT) and sensitive (FDS) bryophytes. The protocol is based on (1) controlled desiccation inside Falcon tubes equilibrated at three different relative humidities that, consequently, induce three different speeds and extents of dehydration and (2) an evaluation of the average percentage of maximal photochemical efficiency of PSII (Fv /fm) recovery after rehydration. Applying the method to 10 bryophytes and 28 tracheophytes from various locations, we found that (1) imbibition of absorbent material with concentrated salt-solutions inside the tubes provides stable relative humidity and avoids direct contact with samples; (2) for 50 ml capacity tubes, the optimal plant amount is 50-200 mg fresh weight; (3) the method is useful in remote locations due to minimal instrumental requirements; and (4) a threshold of 30% recovery of the initial Fv /fm upon reaching RWC ≤ 30% correctly categorises DT species, with three exceptions: two poikilochlorophyllous species and one gymnosperm. The protocol provides a semi-quantitative expression of DHT that facilitates comparisons of species with different morpho-physiological traits and/or ecological attributes.

Mid-infrared carbon dioxide sensor with wireless and anti-condensation capability for use in greenhouses

A mid-infrared carbon dioxide sensor with wireless and anti-condensation capability was experimentally demonstrated for greenhouse application. The sensor included an optical module integrated in a multi-pass gas chamber using the dual-channel detection method to suppress environmental noise. Considering the condensation phenomenon in the greenhouse, the optical chamber was protected with a breathable waterproof coverage. The field test demonstrated that the internal optical framework was kept in stable relative humidity, ensuring the sensor’s applicability in the greenhouse. For wireless communication, received signal strength indication was used to ensure the reliability of link quality and enable smart power regulation. In related experiments, there was a satisfying performance in terms of stability and error detection within the measurement range of 30 − 5000 ppm. Without increasing the integral time, the limit of detection of the sensor was at least 30 ppm, which was acceptable for greenhouse application. A field test was carried out in Town Shelin of Jilin Province, China and the test showed the proposed sensor had relatively good prospect for application in fine agriculture.

Evaluation and Development of a Weighing Chamber by Using Saturated MgCl2 Solution

In recent years, China has suffered a lot from atmospheric particles. Many studies of particles are based on filters. As a result, the accuracy of filter weighing is of great importance. A weighing chamber (1.2 m×0.6 m×0.8 m) was developed and evaluated using saturated MgCl2 solution with a self-made flow control system to maintain constant relative humidity (RH). By evaluating the mass change of blank and aerosol-enriched filters after weighing in different RH, we selected RH of 30%-40% as the range for the proper constant RH. To reach a constant RH, 20 L·min-1 dry air was put through a RH-constant chamber with MgCl2 solution in it. Then, the RH-constant air was put continually into the weighing chamber. After the weighing chamber reached stable RH, the flow rate was adjusted to 5 L·min-1 to maintain the RH. Throughout a one-month test, the weighing chamber maintained 30.1%-34.0% RH while the outside RH changed a lot. We weighed 60 filters with this weighing chamber after equilibration for 24 hours. The standard deviation after three times' weighing was no more than 0.02 mg. compared to other methods, the RH-controlling method of this weighing chamber was simple, stable, easy to maintain, and cost effective.

An Inexpensive, Stable, and Accurate Relative Humidity Measurement Method for Challenging Environments.

In this research, an improved psychrometer is developed to solve practical issues arising in the relative humidity measurement of challenging drying environments for meat manufacturing in agricultural and agri-food industries. The design in this research focused on the structure of the improved psychrometer, signal conversion, and calculation methods. The experimental results showed the effect of varying psychrometer structure on relative humidity measurement accuracy. An industrial application to dry-cured meat products demonstrated the effective performance of the improved psychrometer being used as a relative humidity measurement sensor in meat-drying rooms. In a drying environment for meat manufacturing, the achieved measurement accuracy for relative humidity using the improved psychrometer was ±0.6%. The system test results showed that the improved psychrometer can provide reliable and long-term stable relative humidity measurements with high accuracy in the drying system of meat products.

Application of humidity-regulating tray for packaging of mushrooms

Major postharvest challenge of mushroom includes high transpiration rate resulting in rapid weight loss and the risk of water vapour condensation inside the package, which results in accelerated deterioration in quality and decay. Thus, this study investigated the transpiration behaviour of mushroom under various combinations of storage temperature (4, 12 and 20°C) and relative humidity (RH) (76, 86, 96 and 100%) and assessed the impact of salt embedded humidity-regulating tray on humidity and condensation behaviour in mushroom package at 7°C and 85% RH. The impact of humidity-regulating and control-polypropylene (control-PP) trays on condensation and quality of mushroom was evaluated after 6 days. Despite the saturated RH condition, across all temperatures studied, mushrooms stored at 100% RH lost moisture at the rate of 0.03–0.22mgkg−1s−1. Humidity-regulating tray maintained a stable RH (93%) inside the package and it absorbed 4.1g of water vapour within 6days at 7°C and 85% RH storage condition. Humidity-regulating tray better maintained the quality of mushrooms compared to control-PP tray, but it absorbed only 4.1g of water vapour in 6 days which was not enough to prevent water condensation in the package headspace for mushrooms.

Highly sensitive and stable relative humidity sensors based on WO3 modified mesoporous silica

This study investigates the effectiveness of using WO3 loaded mesoporous silica nanocomposite developed using one step hydrothermal method for measuring relative humidity (RH) at room temperature. On measuring the sensing response, the nanocomposite sensor exhibits excellent linearity, negligible hysteresis, swift response and recovery time, good repeatability, and outstanding stability in 11%–98% RH range. The complex impedance spectra of the sensor at different RHs were used to explore the humidity sensing mechanism. This work could encourage a right approach to blueprint practical humidity sensors with high sensitivity, long stability and fast response/recovery time.