Different Conditions Of Relative Humidity Research Articles

Effect of relative humidity and absorbed water on the ethyl centralite consumption in nitrocellulose-based propellants

The influence of relative humidity on the consumption of ethyl centralite during the degradation of a nitrocellulose-based propellant was investigated. For such energetic material, long term safe storage – maybe decades – is required and various relative humidity conditions can be found. The investigations of chemical integrity based on accelerated ageing by heating and stability tests are not sufficient to characterize the degradation in real conditions. A sample of propellant was aged in different conditions of relative humidity and the residual stabilizer was quantified by HPLC analyses. The stabilizer consumption at ambient temperature was predicted according to the linearized Arrhenius model. We observed a substantial difference in ethyl centralite consumption by comparing the values obtained for distinct humidity conditions. A possible explanation was proposed. Our results allow one to propose an optimum range of relative humidity for long term storage.

Nitrous acid formation on Zea mays leaves by heterogeneous reaction of nitrogen dioxide in the laboratory

Nitrous acid (HONO) is of considerable interest because it is an important precursor of hydroxyl radicals (OH), a key species in atmospheric chemistry. HONO sources are still not well understood, and air quality models fail to predict OH as well as HONO mixing ratios. As there is little knowledge about the potential contribution of plant surfaces to HONO emission, this laboratory work investigated HONO formation by heterogeneous reaction of NO2 on Zea mays. Experiments were carried out in a flow tube reactor; HONO, NO2 and NO were measured online with a Long Path Absorption Photometer (LOPAP) and a NOx analyzer. Tests were performed on leaves under different conditions of relative humidity (5–58%), NO2 mixing ratio representing suburban to urban areas (10–80 ppbv), spectral irradiance (0–20 W m−2) and temperature (288–313 K). Additional tests on plant wax extracts from Zea mays leaves showed that this component can contribute to the observed HONO formation. Temperature and NO2 mixing ratios were the two environmental parameters that showed substantially increased HONO emissions from Zea mays leaves. The highest HONO emission rates on Zea mays leaves were observed at 313 K for 40 ppbv of NO2 and 40% RH and reached values of (5.6 ± 0.8) × 109 molecules cm−2 s−1. Assuming a mixing layer of 300 m, the HONO flux from Zea mays leaves was estimated to be 171 ± 23 pptv h−1 during summertime, which is comparable to what has been reported for soil surfaces.

The effect of the evaporation rate on electrochemical measurements with paper-based analytical devices and its minimisation by enclosure with adhesive tape

In this work, the effect of liquid evaporation on electrochemical measurements with electrochemical paper-based devices (ePADs) is studied. The time evolution of cyclic voltammograms of ferricyanide is used to study the effect of liquid evaporation under different conditions of relative humidity and air currents. Moreover, the enclosure of ePAD channels with adhesive tape is evaluated in terms of minimising the evaporation, as well as increasing the sensitivity in the electrochemical determination of horseradish peroxidase in long-term assays.

Evaluation of hybrid polysaccharide membranes for gas dehydration using on-line mass spectrometry

The removal of water from gas streams, in particular flue gas and biogas, is an important industrial operation. To mimic these industrial dehydration processes, permeation of water vapour, pure gases (CO2, CH4 and N2) and gas mixtures containing 20 vol% CO2 + 80 vol% N2 and 70 vol% CH4 + 30 vol% CO2, at different conditions of relative humidity, was monitored by mass spectrometry. The potential of using hybrid polysaccharide membranes obtained from a low cost carbon source (glycerol) and crosslinked using (3-Glycidyloxypropyl) trimethoxysilane (GPTMS) as silica precursor by a sol-gel method was evaluated. The hybrid membranes developed showed barrier properties to all gases studied, with a gas permeability below 1 barrer, while exhibiting high water permeabilities and selectivities. When process in a biogas mixture, the water permeability was found to be three times higher than water permeability in a flue gas mixture, leading to a H2O/CH4 selectivity much higher than H2O/N2 selectivity. These membranes showed, under close-to-real conditions, that they have the ability to dehydrate mixtures, with the advantage of not losing N2 or CH4, due to the low permeability values of these gases.

Application of photocatalytic paint for destruction of benzo[a]pyrene. Impact of air humidity

AbstractLatex (LX) paint was tested for photocatalytic decomposition of benzo[a]pyrene (BaP) under different conditions of relative humidity (RH), temperature and irradiation. Porcelain trays coated with LX paint were loaded with BaP solution, which was dissolved in acetonitrile. Trays were placed inside the photoreactor and irradiated with UV or a fluorescent lamp. Different conditions of RH and temperature inside the photoreactor were used. BaP preliminarily adsorbed on LX paint surface was decomposed faster at higher temperature and lower RH. For example, at 42 °C and RH 20 % BaP decomposition rate reached 64 %. At same temperature and with RH of 80 % this rate decreased to only 42 %. It was also demonstrated that at high RH (80 %) and under UV irradiation water contact angle on the paint surface was decreasing at a lower rate than under RH of 20 %. It was also proven that BaP could be sufficiently decomposed under irradiation by fluorescent lamp (59 % in comparison to 64 % under same environmental conditions with use of UV light). However, its decomposition rate was approximately 5 times slower than under UV light

Gaseous benzene degradation by photocatalysis using ZnO + Zn2TiO4 thin films obtained by sol-gel process.

The benzene pollutant in gaseous phase was successfully degraded by using ZnO + Zn2TiO4 multicomponent oxide thin films as photocatalysts. The films were obtained with different Ti/Zn ratios (0, 0.20, 0.40, 0.45, 0.50, 0.67, 0.84, and 1) by the sol-gel route. The initial level of benzene concentration was 110 ± 10ppm. The process was carried out under different conditions of relative humidity (RH): 25, 50, and 80% in a batch-type reactor, at room temperature. The results show benzene degradation near to 95% at t = 240min, where the multicomponent oxide semiconductor has a Ti/Zn ratio of 0.67. Meanwhile, with the TiO2 thin films, only a degradation of 70% was reached at the same measurement conditions. This synergistic effect on the photocatalytic activity is a result of the coupling of both semiconductor oxides. An adverse effect on the photocatalytic activity was observed as the relative humidity increases.

Photodegradation of gaseous C6H6 using CdO+CdTiO3 and TiO2 thin films obtained by sol–gel technique

Abstract In this work, TiO2 and CdO + CdTiO3 multicomponent oxide thin films growth was performed with different Ti/Cd ratios (0, 0.20, 0.49, 0.60, 0.65, 0.70 and 1) by the sol–gel route in order to degrade benzene in gas phase with an initial concentration level of 110 ± 10 ppm, under different conditions of relative humidity (RH): 25%, 50% and 80% in a batch type reactor, at room temperature. The results showed a degradation near to 100% at t = 75 min, using the CdO + CdTiO3 multicomponent oxide semiconductor with a Ti/Cd ratio of 0.65. On the other hand, the TiO2 thin films reached only a degradation of 70% in t = 240 min. A decrease of the oxidation process of benzene was observed in all films studied, as the relative humidity increased.

Alternative plasticizers for the production of thermo-compressed agar films

Agar films were produced by thermo-compression using choline chloride (ChCl) as a plasticizer with urea. The three solid components were mixed together with the salt and urea (minor components) added to agar (main component) according to a fixed mass ratio of, respectively, 1.16:1:5. A central composite rotatable design (CCRD) with three parameters, 23, was used to evaluate the effects of temperature (X1; °C), time (X2; min) and applied load (X3; kN) of heat-pressing on the maximum tensile strength (TS) of the films (Y; MPa). Mixtures of urea and agar prepared at a mass ratio of 1:5 did not form homogeneous films suggesting the important plasticizing role of the salt. Heat-pressing the mixtures at more draconian conditions led to much darker and opaque films, with better mechanical resistance (higher values of TS). The most resistant film (∼15MPa) was obtained at 140°C, 20min and 176kN. Selected films, including the optimal, showed similar water sorption profiles and close values of water vapor permeability (∼2.5–3.7×10−9gm−1s−1Pa−1). The fracture behavior and mechanical properties of the films were greatly affected by additional water plasticization when the films were stored at different conditions of relative humidity.

Effect of humidity on the thermal conductivity of porous zirconia ceramics

This study focuses on the role of the water content on the effective thermal conductivity of porous ceramics placed in different conditions of relative humidity. Fully stabilized zirconia samples with variation in the capacity to take up water were prepared by varying the temperature of the thermal treatment. The pore volume fraction of the dried samples decreases from 56% down to 30%. Thermal conductivity measurements were made on samples placed in a chamber where the relative humidity was fixed between 3% and 99%. For all samples, the experimental values of the effective thermal conductivity increase significantly with the water content. Experimental results agree closely to analytical predictions based on the upper limit of the Hashin and Shtrikman expressions for calculating the thermal conductivity of the pores (constituted by air and water) and Landauer's effective medium expression for calculating the effective thermal conductivity of the material.

The hydrolytic effect of moisture and hygrothermal aging on poly(butylene succinate)/organo-montmorillonite nanocomposites

The study of hydrolysis on biodegradable poly(butylene succinate) (PBS) is essential to predict the materials properties in a humid environment. In this study, PBS nanocomposites were exposed to different conditions of relative humidity (RH) and temperature. The moisture uptake increased with organo-montmorillonite (OMMT) loading and the RH of the testing environment. The exposure of PBS and the nanocomposites to a humid environment caused changes in the mechanical properties. The hydrolytic degradation becomes more pronounced upon hygrothermal aging at high temperature, whereby premature failure occurred. PBS nanocomposites were found to exhibit a better hydrolytic stability than neat PBS. The degradation was evaluated through Fourier transform infrared (FTIR) spectroscopy and gel permeation chromatography (GPC). A drastic reduction in the molecular weight of PBS has revealed the occurrence of degradation after exposure to moisture and heat. This has led to an alteration of the thermal behavior as investigated using differential scanning calorimetry (DSC).

Exploring the limits for the survival of DNA in blood stains

It is generally recognized that usable DNA may be retained in dry biological stains for years. We have explored the environmental limits for this property. Air-dried blood stains were incubated at different conditions of relative humidity (RH) and temperature. The quality of the extracted DNA was assessed by the ability to amplify 273 bp and 1600 bp DNA fragments by PCR, and by quantitative estimation of a 147 bp DNA fragment using real time PCR. Despite the fact that the availability of water is important for processes that degrade DNA, no significant difference was observed in the stability of DNA at 50%, 80% or 93% RH at room temperature or at 35 °C, and even the 1600 bp fragment was amplifiable after one year. Microbial growth was not observed at these conditions and the number of template molecules did not drop significantly over time. At 100% RH, however, microbial growth was observed after varying amounts of time. This may explain the decreased stability of DNA observed at these conditions. Even so, the 273 bp fragment was amplifiable for at least 3 months, and the 1600 bp fragment for at least two months. Microbial growth was not observed at higher temperatures (45–65 °C) at 100% RH, and the 1600 bp fragment was amplifiable after eight months at 45 °C, but only survived for one month at 55 °C or 65 °C. Thus DNA remains amplifiable in blood stains for many months, even at extreme RH and temperatures up to 45 °C. Even in humid climates the average RH is usually not more than 80% and RH rarely exceeds 93%; therefore we conclude that normal climatic conditions are not critical for the long time survival of DNA in untreated blood stains.

XPS study of nitrogen dioxide adsorption on metal oxide particle surfaces under different environmental conditions

The adsorption of nitrogen dioxide on gamma aluminium oxide (gamma-Al(2)O(3)) and alpha iron oxide (alpha-Fe(2)O(3)) particle surfaces under various conditions of relative humidity, presence of molecular oxygen and UV light has been investigated. X-Ray photoelectron spectroscopy (XPS) is used to monitor the different surface species that form under these environmental conditions. Adsorption of NO(2) on aluminum oxide particle surfaces results primarily in the formation of surface nitrate, NO(3)(-) with an oxidation state of +5, as indicated by a peak with binding energy of 407.3 eV in the N1s region. An additional minority species, sensitive to the presence of relative humidity and molecular oxygen, is also observed in the N1s region with lower binding energy of 405.9 eV. This peak is assigned to a surface species in the +4 oxidation state. When irradiated with UV light, other species form on the surface. These surface-bound photochemical products all have lower binding energy, between 400 and 402 eV, indicating reduced nitrogen species in the range of N oxidations states spanning +1 to -1. Co-adsorbed water decreases the amount of these reduced surface-bound products while the presence of molecular oxygen completely suppresses the formation of all reduced nitrogen species on aluminum oxide particle surfaces. For NO(2) on iron oxide particle surfaces, photoreduction is enhanced relative to gamma-Al(2)O(3) and surface bound photoreduced species are observed under all environmental conditions. Complementing the experimental data, N1s core electron binding energies (CEBEs) were calculated using DFT for a number of nitrogen-containing species in the gas phase and adsorbed on an Al(8)O(12) cluster. A range of CEBEs is calculated for various nitrogen species in different adsorption modes and oxidation states. These calculated values are discussed in light of the peaks observed in the XPS N1s region and the possible species that form following NO(2) adsorption and photoreaction on metal oxide particle surfaces under different conditions of relative humidity, presence of molecular oxygen and UV light.

Reactive Binders in Detergent Granulation: Understanding the Relationship between Binder Phase Changes and Granule Growth under Different Conditions of Relative Humidity

The increasing tendency to enhance consumer products with added functionality is leading to ever more complex products that are manufactured at large scale in conventional processes. Hence, it is important that process operating conditions are matched to the product requirements. We report on the fundamental characteristics of the reactive binder, LAS acid (HLAS), used in detergent granulation, in relation to its wetting behavior and viscosity as it is neutralized by its reaction with sodium carbonate, and how the phase changes are affected by relative humidity (RH) and temperature, in order to establish the relationship between the binder phase changes and granule formation and growth. We have found that the higher the degree of neutralization, the lower the tendency of the liquid to wet the particles (the binder behaves as a sticky paste) and that wetting behavior is strongly dependent on RH. The latter highlights the importance of controlling the environmental conditions during processing and storage of the materials.

Qualidade do café natural e despolpado após diferentes tipos de secagem e armazenamento

Para se comparar as alterações na qualidade do café natural e despolpado em condições de umidades relativas de 60 e 80% e temperatura controlada de 23 °C aos 90 e 180 dias de armazenamento, realizou-se este trabalho no Departamento de Engenharia e no Pólo de Tecnologia em Pós-Colheita do Café da Universidade Federal de Lavras. A colheita do café, variedade Topázio, foi seletiva, enquanto uma parte foi despolpada e a outra processada de forma natural; no entanto, uma parcela de cada tipo de café foi conduzida para a secagem em terreiro e a outra parcela para secagem com temperaturas de 40 e 60 °C; após a secagem, o café foi armazenado em ambiente hermético mantendo-se constantes as umidades relativas de 60 e 80%. Para avaliação da qualidade foram feitas análises sensoriais, teste de acidez graxa e avaliação quantitativa da cor. Os resultados obtidos no presente trabalho permitem concluir que: a acidez graxa aumenta ao longo do tempo de armazenamento nas condições de 60 e 80% de umidade relativa; a descoloração do café é mais intensa ao longo do tempo de armazenamento para as condições de 80% de umidade relativa; aos 180 dias de armazenamento, a análise sensorial do café é menos afetada pela interação secagem, processamento e armazenamento, nas condições de 60% de umidade relativa.

Analysis of the voltage coefficient of high value standard resistors

Standard resistors in the field 100 MΩ–1 TΩ, normally available in National and secondary laboratories, were measured and characterized with respect temperature and applied voltage [F. Galliana, G. Boella, High value resistors: study of their behaviour versus applied voltage”, in: Proc. of the 16th IMEKO World Congress, Wien, Austria, September 25–28, 2000; F. Galliana, E. Gasparotto, R. Cerri, Evaluation of the temperature and voltage coefficients of high value resistors, IEN Technical Report no. 565, February, 1999]. The measurements were carried out with a system based on the use of a digital multimeter (DMM) [F. Galliana, G. Boella, The electrical dc resistance scale from 100 kΩ–1 TΩ, IEEE Trans. Instrum. Meas. 49 (5) (2000) 959–963; F. Galliana, G. Boella, P.P. Capra, Calibration of standard resistors in the field 10 MΩ–1 TΩ by means of a digital multimeter, in: Proc. of IMEKO TC-4, vol. I, Naples, September 1998. pp. 191–195; G. Boella, F. Galliana, Comparison of different methods for the calibration of standard resistors in the range 10 MΩ–1 GΩ, in: Proc. of 8th Int. Metrology Conf. Metrologie 97, Besancon, France, October 20–24, 1997. pp. 457–461]. Most standard resistors showed a behaviour versus applied voltage that can be represented by a function having a linear plus a quadratic component. Some of them were also measured at different conditions of relative humidity: the influence of this environmental parameter on the voltage behaviour of the standards has been analyzed. An evaluation of the influence of the variation of the leakage resistances was also be done.

The Effects of Relative Humidity and Super-Disintegrant Concentrations on the Mechanical Properties of Pharmaceutical Compacts

The influence of the composition and the relative humidity on the properties of pharmaceutical compacts prepared from mixtures of three excipients and three super-disintegrants was evaluated. Various amounts of super-disintegrant and different conditions of relative humidity during the storage were used to study mechanistically the disintegration process and to connect it to compact's mechanical properties. Three point single beam test was used to measure tensile strength and Young's modulus of compacts containing various amount of disintegrant and stored under various relative humidity. The presence of moisture within pharmaceutical compacts containing a disintegrant influences drastically their mechanical properties. Then, the results are related to micro-cracks visualized by MEB.

Role of Fabric Structure on Moisture Retention and its Effect on Concrete Strength

This work aims at studying the effect of textile structures on the water retentivity and implications of retentive structures on civil applications. Different structures are analyzed for their water retentivity and drying rate at different conditions of relative humidity (RH) and temperature. Non-woven structures are, in general, more retentive than the woven, under different conditions of test. The possible mechanism behind such a behavior is proposed. Investigations have been carried out on the effect of fabric structure on compressive strength of concrete wrapped and unwrapped with different textile structures by immersing in water for 10 min in an interval of 24 and 48 h. The results show that the concrete wrapped with non-woven fabric gives strength improvement of 2.5 N/mm2 higher than that of woven fabric of the same gram per square meter (GSM) when water is sprayed every day and 1.75 N/mm2 higher when water is sprayed on an alternate day curing cycle.

Polimeric Electrolyte Membrane Fuel Cells: Characterization Test Under Variable Temperature and Relative Humidity Conditions

The aim of this work is the performance study of a polimeric electrolyte membrane stack. Extreme conditions of temperature and relative humidity, such as those that may be found in practical situations (i.e., automotive), have been considered. The research has been developed by Department of Energetics of Politecnico di Milano in collaboration with Nuvera Fuel Cells Europe, under confidential agreement. In order to select the proper electrolyte that can be used to build a stack suitable for automotive applications, three different types of material have been tested in single fuel cells, under different conditions of temperature and relative humidity by mean of a climatic chamber. Both traditional (Nafion®) and new materials have been tested in single cells of 16cm2 of active area. The three electrolyte materials have been tested also by measuring the protonic conductance, in different conditions of relative humidity. After these tests, an electrolyte has been chosen that was made with a coated catalyst membrane having a thickness of 35μm, which has been used to build a six-cell stack with an active area of 500cm2. The performances of the stack have been evaluated, in continuous operation, with air temperatures ranging from 50°C to −40°C. A series of start-up tests has been carried out with an air temperature ranging between 0°C and −25°C.

Effect of air humidity on the growth and morphology of Hydrangea macrophylla L.

Hydrangea macrophylla cv. Leuchfeuer is grown in the greenhouse under two different conditions of relative humidity (vapour pressure deficits (vpd) of 1.6 and 0.6 kPa). The relative humidity does not affect the initiation or the release of new pairs of leaves. However, it modifies the size of the plant and the total leaf area. After 79 days of growth, a decrease in the relative humidity from 80% to 50% leads to a 38% decrease in height growth and a 30% decrease in leaf growth. The effect of relative humidity on the growth of H. macrophylla influences the management of the size of the plant and, therefore, the quality of the product marketed. It is likely that it will have an effect on floral development as well.

Umidade de equilíbrio de painéis de madeira

Este estudo teve como objetivo a determinação da umidade de equilíbrio de painéis de madeira numa câmara de climatização e comparação dos seus valores com os obtidos através da equação de Nelson. O trabalho foi desenvolvido na Unidade Experimental de Produção de Painéis de Madeira da Universidade Federal de Lavras. Foram utilizadas amostras de aglomerado, compensado multilaminado e sarrafeado, chapa dura, OSB (Oriented Strand Board) , MDF (Medium Density Fiberboard), HDF (High Density Fiberboard), madeira-cimento e madeira-plástico, sendo esses produtos de escala industrial e experimental. As dimensões dos corpos-de-prova foram de 2,60 cm de largura por 2,60 cm de comprimento. As espessuras foram aquelas mais utilizadas comercialmente de cada produto, sendo utilizadas cinco repetições por painel. Os corpos-de-prova foram pesados e levados para uma câmara de climatização, onde foram submetidos a diferentes condições de umidade relativa (90, 80, 70, 60, 50 e 40%) e uma temperatura constante de 30 ºC. Determinaram-se a histerese e a umidade de equilíbrio, que variaram de 40 a 90%. Os resultados indicaram que a equação de Nelson se mostrou eficiente na estimativa da umidade de equilíbrio e que não existe em média diferença de histerese entre os produtos estudados, mostrando que todos apresentam a mesma estabilidade dimensional. Observou-se, também, que o revestimento dos painéis não afetou a umidade de equilíbrio.