Relative Humidity Relationship Research Articles

Assessment of the performance of Cromarty's equation to predict seed equilibrium moisture content during drying

For conventional seed (gene)banking of orthodox seeds, it is essential to effectively dry the seeds and maintain a low moisture content (MC). Cromarty's equation describes the MC and relative humidity (RH) relationship of drying seeds, based on their oil content, and can be used to predict the MC seeds would reach when dried to equilibrium in a controlled environment (RH, temperature). However, the equilibrium MC-RH relationship ('isotherm') varies not only between seeds of different species and depending on temperature, but also on whether seeds are losing (desorbing) or gaining (adsorbing) moisture. The reliability of Cromarty's equation in predicting the equilibrium MC for drying different seed species was examined and compared with the Guggenheim-Anderson-De Boer (GAB) equation, to model both desorption and adsorption data. Cromarty's equation provided a good fit to the desorption data for oilseed rape and barley (R 2 = 0.98). For yellow mustard, seed MC was overestimated and for lupin, wheat, buckwheat and pea, the MC equilibria predicted by Cromarty's equation were closer to the adsorption data. Overall, the GAB equation provided a better fit of the data. While Cromarty's equation is a useful tool for estimating the MC of seeds under a given environment, it should be used with caution in critical situations.

A meta-analysis result: Uneven influences of season, geo-spatial scale and latitude on relationship between meteorological factors and the COVID-19 transmission

Meteorological factors have been confirmed to affect the COVID-19 transmission, but current studied conclusions varied greatly. The underlying causes of the variance remain unclear. Here, we proposed two scientific questions: (1) whether meteorological factors have a consistent influence on virus transmission after combining all the data from the studies; (2) whether the impact of meteorological factors on the COVID-19 transmission can be influenced by season, geospatial scale and latitude. We employed a meta-analysis to address these two questions using results from 2813 published articles. Our results showed that, the influence of meteorological factors on the newly-confirmed COVID-19 cases varied greatly among existing studies, and no consistent conclusion can be drawn. After grouping outbreak time into cold and warm seasons, we found daily maximum and daily minimum temperatures have significant positive influences on the newly-confirmed COVID-19 cases in cold season, while significant negative influences in warm season. After dividing the scope of the outbreak into national and urban scales, relative humidity significantly inhibited the COVID-19 transmission at the national scale, but no effect on the urban scale. The negative impact of relative humidity, and the positive impacts of maximum temperatures and wind speed on the newly-confirmed COVID-19 cases increased with latitude. The relationship of maximum and minimum temperatures with the newly-confirmed COVID-19 cases were more susceptible to season, while relative humidity's relationship was more affected by latitude and geospatial scale. Our results suggested that relationship between meteorological factors and the COVID-19 transmission can be affected by season, geospatial scale and latitude. A rise in temperature would promote virus transmission in cold seasons. We suggested that the formulation and implementation of epidemic prevention and control should mainly refer to studies at the urban scale. The control measures should be developed according to local meteorological properties for individual city.

Bioecology of the tea thrips, Scirtothrips bispinosus Bagnall (Thysanoptera: Thripidae) infesting tea in south India

Investigations were carried out on the life history and seasonal abundance of the thrips, Scirtothrips bispinosus infesting tea at Coonoor, The Nilgiris, Tamilnadu. The total developmental duration of females from egg to adult stage was 18.15±0.23, 12.55±0.15 and 10.30±0.23 days at 20, 25 and 30oC respectively. The net reproductive rate (Ro), mean generation time (Tc), intrinsic rate of natural increase (rm), finite rate of increase (ë) and weekly multiplication (Wm) rates were high at 25oC followed by 30oC and 20oC. Multiple regression analysis revealed that population density of S. bispinosus showed a negative relationship with rainfall (-0.266), maximum temperature (-38.839) and maximum relative humidity (-3.356) and positive relationship with minimum temperature (63.205), minimum relative humidity (1.686) and sunshine period (2.887). Incidence of thrips was high in the fields recovering from pruning followed by second, third and fourth year in a pruning cycle. The number of thrips per shoot was significantly higher on the plucking table when compared to the shoots present below the plucking table and side branches. In the tea plantations of South India, four species of predatory mites (Amblyseius cucumeris, A. fallacies, A. degenerans and Balaustium sp.), two species of predatory thrips (Franklinothrips vespiformis and Leptothrips mali), an anthocorid predator (Orius sp.) and one parasitoid (Trichogramma sp.) were found feeding and parasitizing on tea thrips, S. bispinosus.

Highly accurate particulate matter detection assisted by an air heater based on a silver nanowire film

Recently, many studies have been carried out to solve the particulate matter pollution problem. However, the detection accuracy for particulate matter in the atmosphere remains unsatisfactory due to the influence of the air relative humidity. Herein, we report a Ag nanowire film air heater to enhance the detection accuracy through internal heating. From air temperature and air relative humidity relationship analysis, it has been found that the Ag nanowire film air heater can form the most suitable air relative humidity in the detection system, thereby enhancing the detection accuracy. Consequently, the Ag nanowire film air heater-assisted light scattering particulate matter detector has achieved tremendous enhancement in its detection accuracy, which is comparable with the data obtained by the beta gauge method. Film resistance plays a key role in internal air temperature distribution and the resultant air relative humidity at given voltages. To achieve the most suitable air relative humidity for continuous online monitoring, response time and power consumption should be balanced. Therefore, guidance for designing Ag nanowire films with proper resistance used in an optional-sized detector has been given for quick response, high accuracy and low power consumption. This work is of significance for providing insight for future studies in particulate matter detection and pollution remediation.

Fabrication of chitosan and calcium carbonate bio-crystals for humidity sensor prepared from annealed shrimp shells and eggshells

We reported the catalyst-free humidity sensor prepared from shrimp shells and eggshells. The annealed shrimp shells and eggshells were ground to powder and mixed together at various ratios. The samples were characterized and investigated by X-ray diffraction technique (XRD), Scanning electron microscope (SEM) and humidity sensing measurements. As a result, XRD patterns of shrimp shells and eggshells show chitosan and CaCO3 structures, respectively. Their SEM images indicate massive agglomeration. Moreover, the humidity sensor demonstrates the highest sensitivity of shrimp shells and eggshells at the ratio of 1:1 for 4.81 at 85%RH. The resistance and relative humidity relationship indicates non-linear inverse behavior. However, the resistance of the samples decreases at higher relative humidity.

Air and Moisture Transport Properties of Low‐Oil DDGS

Distillers dried grains with solubles (DDGS) are widely used as feed for cattle, dairy, and swine because of their protein, fiber, amino acids, fat, and other vital nutrients. Corn ethanol plants in the United States recently have started extracting oil from DDGS to gain additional profit, thus producing low‐oil DDGS. So far, there has been no comprehensive study reported with bulk handling and flowability properties of low‐oil DDGS. We measured the air resistance, moisture diffusivity, and air permeability properties for low‐oil DDGS at different temperature and relative humidity conditions, along with some important physical and chemical properties. Physical property comparisons between regular and low‐oil DDGS showed differences in key properties such as particle size, color, density, porosity, and angle of repose. The modified Henderson model predicted the equilibrium moisture content (EMC)–equilibrium relative humidity (ERH) relationship of low‐oil DDGS with a low standard error of regression value (0.008); it showed no pattern in the residuals and was judged the most appropriate model tested for EMC‐ERH predictions. Results of EMC‐ERH nonlinear modeling were used to define conditions for moisture diffusivity. Moisture diffusivities of low‐oil DDGS at varying drying temperatures ranged from 0.74 × 10−11 to 1.77 ×10−11m2/s. The properties are important for understanding and modeling heat and moisture transport through and flow properties of low‐oil DDGS.

Hygroscopic moisture content: determination and correlations

Hygroscopic moisture content of fine-grained soil represents the water adsorbed by the negatively charged clay platelets when the oven-dried soil is exposed to an atmosphere with different levels of humidity, which is a variable. Hygroscopic moisture content has been linked with many clay mineralogical parameters in predictive geotechnical engineering. However, there appears to be no standard codal provisions to quantify this property. This paper uses the modified rectangular hyperbolic representation of the adsorbed water content against time of exposure to an environment with 100% relative humidity relationship to quantify the hygroscopic moisture content. The proposed method is very simple and fairly accurate. The hygroscopic moisture contents so predicted corresponding to 100% relative humidity have been shown to have one-to-one correspondence with the values obtained through actual time-consuming measurements. By virtue of common dependency factors, it is shown that the hygroscopic moisture content at 100% relative humidity of fine-grained soils can be uniquely related with their liquid limits and equilibrium sediment volumes. Furthermore, instead of a time-consuming method of determining the hygroscopic moisture content, a simple method of predicting the same knowing their liquid limits has been proposed.

Adsorption Studies of Radish Leaf Powder

Radish leaves ( Raphanus sativus ) powder fractions was subjected to moisture adsorption isotherms at different isothermal temperature conditions from 15-45°C with an equal interval of 10°C. The sorption data obtained in gravimetric static method under 0.11–0.90 water activity conditions were subjected for sorption isotherms and found to be typical sigmoid trend. Experimental data were assessed for the applicability in the prediction through sorption models fitting and found that Polynomial and GAB equations performed well over all fitted models in describing equilibrium moisture content – equilibrium relative humidity (EMC–ERH) relationships for shelf stable dehydrated radish leaf powder, over the entire range of temperatures condition under study. The net isosteric heat of sorption, differential entropy and free energy were determined at different temperatures and their dependence was seen with respect to equilibrium moisture content.

Moisture sorption characteristics of dairy whitener at different temperatures

The sorption isotherms describe the equilibrium relationship between water activity (a w ) and moisture content of the food at constant temperatures and pressures. The knowledge of sorption isotherms of a food product is essential for product and process development in solving engineering problem such as equipment design, drying and storage condition selection as well as predicting the shelf life of food. In the present investigation, the fraction of adsorption and desorption isotherms of dairy whitener were drawn at three temperatures viz., 30, 40 and 50 o C. A gravimetric static method was used approximately between 11– 92% relative humidity for sorption isotherms that were found to be typical type II sigmoid shape. The equilibrium moisture content (EMC) for dairy whitener within the range of 0.113 to 0.923 was higher at 30 o C as compared to 40 and 50 o C. At the temperatures of 30, 40 and 50 o C, the equilibrium moisture content of dairy whitener increased from 2.837 to 47.263, 2.646 to 28.48 and 2.222 to 17.423 g/ 100 g solids respectively. Experimental data were fitted to five mathematical models viz. Modified Mizrahi, Caurie, Oswin, Halsey and Guggenheim–Anderson–de Boer (GAB). It was found that GAB model was acceptable in describing equilibrium moisture content–equilibrium relative humidity (EMC–ERH) relationships over the entire range of selected temperatures. Monolayer moisture content of dairy whitener decreased with increasing temperature from 3.355 at 30 o C to 2.199 g/100 g of solids at 50 o C.

Impact of Sequential Ammonia Fiber Expansion (AFEX) Pretreatment and Pelletization on the Moisture Sorption Properties of Corn Stover

Combining ammonia fiber expansion (AFEX™) pretreatment with a depot processing facility is a promising option for delivering high-value densified biomass to the emerging bioenergy industry. However, because the pretreatment process results in a high moisture material unsuitable for pelleting or storage (40% wet basis), the biomass must be immediately dried. If AFEX pretreatment results in a material that is difficult to dry, the economics of this already costly operation would be at risk. This work tests the nature of moisture sorption isotherms and thin-layer drying behavior of corn (Zea mays L.) stover at 20°C to 60°C before and after sequential AFEX pretreatment and pelletization to determine whether any negative impacts to material drying or storage may result from the AFEX process. The equilibrium moisture content to equilibrium relative humidity relationship for each of the materials was determined using dynamic vapor sorption isotherms and modeled with modified Chung-Pfost, modified Halsey, and modified Henderson temperature-dependent models as well as the Double Log Polynomial (DLP), Peleg, and Guggenheim Anderson de Boer (GAB) temperature-independent models. Drying kinetics were quantified under thin-layer laboratory testing and modeled using the Modified Page's equation. Water activity isotherms for non-pelleted biomass were best modeled with the Peleg temperature-independent equation while isotherms for the pelleted biomass were best modeled with the Double Log Polynomial equation. Thin-layer drying results were accurately modeled with the Modified Page's equation. The results of this work indicate that AFEX pretreatment results in drying properties more favorable than or equal to that of raw corn stover, and pellets of superior physical stability in storage.

Moisture sorption characteristics of freeze dried whey-grape beverage mix.

Moisture sorption isotherms of freeze dried whey-grape beverage powder were determined at 20, 30 and 40°C. A gravimetric static method was used under 0.11-0.85 water activity range and the sorption isotherms were found to be Type II. Various mathematical models were fitted to experimental data and it was found that Peleg model suits best in describing the equilibrium moisture content-equilibrium relative humidity relationships of instant whey-grape beverage mix over the range of temperatures studied. The net isosteric heat of sorption varied between 5.22 and 1.12KJ/mol at moisture level varying between 1 and 9% db. At moisture content below 1% (db) the isosteric heat of sorption increased sharply for freeze dried whey-grape beverage powder and value of 49.08KJ/mol was estimated.

U.S. Air Force Perfluoropolyalkylether Experiences

The U.S. Air Force Research Laboratory (AFRL) received the first sample of perfluoropolyalkylether (PFPAE) liquid lubricant outside of private industry in the 1960s. The unique behavior of PFPAE fluids includes their excellent thermal stability (up to 345°C with appropriate additives) and excellent viscosity-temperature properties for the linear structures. Military applications are often cutting-edge technology requiring these unique properties, but other undesirable behavior such as tribo-corrosion has required investigations into basic understanding of PFPAE fluids. From the 1960s on, Air Force scientists have investigated many aspects of their behavior as summarized here. This presentation discusses various types of PFPAEs commercially available and highlights studies on elastohydrodynamic lubrication film formation, model compounds, additives, relative humidity relationship to wear, and potential U.S. military program applications.

Moisture sorption isotherms and heat of sorption of instant (soluble) green tea powder and green tea granules

Moisture adsorption isotherms of green instant tea powder and green tea granules were determined at 20, 30, 40 and 50 °C. A gravimetric static method was used under 0.11–0.90 water activity ranges for the determination of sorption isotherms that were found to be typical type II sigmoid. Experimental data were fitted to various mathematical models and found that Peleg model suits best in describing equilibrium moisture content–equilibrium relative humidity (EMC–ERH) relationships for instant green tea samples as well as green tea granules, over the entire range of temperatures. The net isosteric heat of sorption was determined from the equilibrium data at different temperatures. The isosteric heat of sorption varied between 48.54 and 44.71 kJ/mol at moisture levels varying between 1 and 9 g/g dry matter for instant green tea powder and 47.96 and 44.10 kJ/mol at moisture level varying between 0.2 and 1.4 g/g dry matter for green tea granules.

Moisture sorption characteristics of mango–soy‐fortified yogurt powder

Moisture adsorption isotherms of plain yogurt, mango–soy‐fortified yogurt (MSFY) and MSFY containing 0.4% gelatin stabilizer (MSFYG) powder were determined at 20, 30, 40 and 50°C. A gravimetric static method was used under 0.11–0.81 water activity ranges for the determination of sorption isotherms that were found to be typical type II sigmoid. Experimental data were fitted to five mathematical models viz. modified Henderson, modified Chung–Pfost, Oswin, Smith and Guggenheim–Anderson–de Boer (GAB). It was found that both Oswin and GAB models were acceptable in describing equilibrium moisture content–equilibrium relative humidity (EMC–ERH) relationships for yogurt powder samples over the entire range of temperatures.

Does Low-Temperature Pest Management Cause Damage? Literature Review and Observational Study of Ethnographic Artifacts

Preventive low-temperature treatment as a means of pest control during the relocation of the ethnographic collections of the National Museum of the American Indian afforded the opportunity to undertake an observational study of potential damage from this treatment. Does low temperature harm materials thought to be vulnerable? What are the possible causes of damage from this treatment? The study revealed no visible damage to any of the materials treated, although the literature suggests that minor changes on a molecular level are likely. The literature also indicates that the effects of changing relative humidity and water relationships are less of a threat than effects related to low temperature alone, such as shrinkage, embrittlement, and molecular alteration. The first part of the article discusses the threat (real or imagined) of various damage mechanisms, and the second part addresses several categories of vulnerable artifacts in relation to these damage mechanisms. The observational study and literature review indicate that low-temperature pest control may be appropriate for a wider range of materials than was previously assumed.

PH—Postharvest Technology: Comparison of Seven Equilibrium Moisture Content Equations for some Medicinal and Aromatic Plants

In this research, seven equilibrium moisture content (EMC) and equilibrium relative humidity (ERH) equations (modified Henderson, Chung–Pfost, Modified Halsey, Henderson, Chen–Clayton, Iglesias–Chirife and modified Oswin) are compared on their ability to fit data for some medicinal and aromatic plants. Thirteen data sets comprising 13 plants are used. Comparisons are based on standard error of estimate, coefficient of determination, residual sum of square and residual plots. Both the modified Halsey and the modified Oswin equations were found as the most versatile models to accurately describe the equilibrium moisture content and equilibrium relative humidity (EMC/ERH) relationships for medicinal and aromatic plants. The modified Henderson equation is a good model for fennel and cinnamon. The Chung–Pfost equation is suitable for muscat, coriander, ginger and cinnamon. The Iglesias–Chirife, Henderson and Chen–Clayton equations are among the least successful models for medicinal and aromatic plants, respectively.

Moisture sorption isotherms of some Nigerian hides, skins and leather

The moisture content-equilibrium relative humidity relationships of hides, skins and tanned skins (leather) at room temperature (26–29°C) were determined and compared. Sorption isotherms for untanned skins and hides are more similar to each other than they are to the sorption isotherms for tanned skins. Vegetable tanned skin generally adsorbs less water than chrome tanned skin. It is recommended that untanned hides and skins, chrome and vegetable-tanned skins be stored at or below 16, 11 and 7% moisture content respectively.

A mean moisture content-equilibrium relative humidity relationship for nine varieties of wheat

A mean moisture content-equilibrium relative humidity relationship for nine varieties of wheat at 25°C is presented, for which the curves were fitted by eye. The mean safe storage moisture content in equilibrium with 70% relative humidity (r.h.) for all the wheat varieties adsorbing moisture was 14.7% (wet weight basis) but if varietal differences and errors in measurement are taken into account, the moisture content of stored wheat may need to be as low as 13% to be safe from attack by mites. The hysteresis between adsorption and desorption reached a maximum of 0.7% moisture content at 40–50% r.h. Hysteresis was found to be statistically significant up to 75% r.h. Equilibrium moisture contents were calculated from data transformed using the Chung and Pfost equation and compared with the measured moisture contents.

The relationship between moisture content and equilibrium relative humidity of pig feed

The moisture content-equilibrium relative humidity relationships at 5, 15 and 25°C of 3 pig meals and pellets made mostly from barley meal and wheatings, with various proportions of soya meals, were very similar to each other. The moisture content in equilibrium with 70% r.h. at 25°C was about 14%, similar to that for cereal grains but these pig feeds should be stored at or below 12% mositure content at this temperature, to avoid the risk of the development of mites.

The moisture content-equilibrium relative humidity relationship of cocoa beans

The moisture content-equilibrium relative humidity relationships for cocoa beans grown in nine different countries were similar to each other, and the maximum safe storage moisture content in equilibrium with 70% relative humidity was between 6.0 and 7.9% at 25°C. There was a large variation between the moisture content of individual beans within each sample, the maximum standard deviation observed in a sample of thirty beans being 0.97, after the moisture content had been increased by adding water.