Search results for "Humidity"
showing 10 items of 291 documents
Hydration and water holding properties of cross-linked lignite humic acids
2014
Abstract Lignite and lignite humic acids, which are used as soil amendments sometimes, are supposed to improve soil properties such as water holding capacity. The structure of those materials is composed of various organic molecules stabilized mostly by weak interactions. Therefore, excess of water causes only partial swelling, but most of the physical structure is destabilized. This accelerates the desiccation and hampers their application as natural hydrogel-like substances. In order to stabilize the structure of lignite humic acids and improve the water holding capacity, we applied formaldehyde cross-linking procedure based on covalent coupling of aromatic humic acids moieties. By combin…
Non-Isothermal Mathematical Model of Wood and Paper Drying
2002
A mathematical model of wood or paper drying based on a detailed consideration of both heat and moisture transport phenomena is proposed. By averaging we express the model as a sequence of initial value problems for systems of two first order nonlinear ordinary differential equations. This mathematical model makes it possible to efficiently investigate the drying process of a thin wood plate or paper sheet for varying temperature and humidity conditions in the surroundings. In particular, we have considered the optimization of the heat regime over a series of steam-heated cylinders in a papermaking machine.
Gravimetric measurement of water vapour sorption, moisture and dry mass
2004
The gravimetric measurement of the moisture content of solids is discussed in comparison to other usual methods. Results of measurements of silica gel are reported. Furthermore, we inform on standardisation work.
Physical modeling of heat and moisture transfer in wet bio-sourced insulating materials.
2018
Simultaneous heat and moisture transfers in bio-sourced insulating materials are significant phenomena in thermal metrology. The present study focuses on these phenomena by experimental and numerical approaches based on the asymmetric hot-plate method. In this paper, a bio-sourced insulating material based on flax fibers is developed. The thermal and hygric properties of the sample are then investigated in the humid atmosphere. The temperature is maintained at 30 °C, and the relative humidity varies between 30% and 90% RH. A physics-based model of simultaneous heat and moisture transfer is developed for thermal conductivity estimation. This model is discretized with finite difference method…
Analysis of gas sensors array signals for evaluation of mold contamination in buildings
2018
Mold is considered to be one of the most important features of Sick Building Syndrome (SBS) and is an important problem in building sector. In numerous cases it is caused by the rising moisture of building envelopes and overstated humidity of indoor air. Fungal contamination is normally evaluated using standard biological methods which are time-consuming and require a lot of manual labor. But also, fungi emit Volatile Organic Compounds (VOC) that can be detected in the indoor air using several techniques of detection e.g. chromatography. VOCs can be also detected using gas sensors arrays. All arrays of sensors generate particular electric signals that ought to be analyzed using statistical …
Association between climate and new daily diagnoses of COVID-19
2020
AbstractBackgroundAlthough evidence is accumulating that climate conditions may positively or negatively influence the scale of coronavirus disease 2019 (COVID-19) outbreaks, uncertainty remains concerning the real impact of climate factors on viral transmission. Methods. The number of new daily cases of COVID-19 diagnosed in Verona (Italy) was retrieved from the official website of Veneto Region, while information on daily weather parameters in the same area was downloaded from IlMeteo website, a renowned Italian technological company specialized in weather forecasts. The search period ranged between March 1 to November 11, 2020. The number of new daily COVID-19 cases and meteorological da…
Water transport in epoxy/MWCNT composites
2013
Moisture and water uptake of epoxy/multi-wall carbon nanotube (MWCNT) composites was studied in a wide range of atmosphere relative humidity and temperatures. Addition of up to 1 wt.% of MWCNTs into the neat epoxy resulted to the twofold decrease of the diffusivity, while the levels of moisture/water uptake remained unchanged. The positive effect on the reduction of the diffusion coefficient diminishes with the increase of temperature. Differences in the water transport properties and plasticization ability of the neat polymer and its nanocomposites are explained by the free volume considerations and the polymer–water interactions, which are verified by the results of thermomechanical analy…
Moisture absorption, thermal conductivity and noise mitigation of clay based plasters: The influence of mineralogical and textural characteristics
2016
Abstract Three pre-mixed clay based plasters successfully employed in green building practices in several European countries (Spain, France, Germany, and United Kingdom), mainly used for interior wall coating and finishing, were tested in this paper. Their compositional and textural characteristics as well as plastic behaviour were investigated through a multi-analytical approach in a previous paper. A natural earth (Terra Rossa red soil sampled in north-western Sicily), theoretically appropriate for the production of earthen plaster, was also subjected to the same analytical routine and compared with the three commercially available products. Humidity control capacity by the determination …
A new approach to studying sponge cake aroma after storage in treated paper and plastic packaging by direct gas chromatography–olfactometry (D-GC–O)
2007
The objective of this study was to use D-GC–O to compare the global odour of a sponge cake flavoured with either a ‘viennoiserie’ aromatic note or a simplified mixture of aroma compounds (used for physicochemical studies), then stored in a glass packaging (inert and impermeable) or in pouches made with treated papers or with plastic packaging, in accelerated ageing conditions (high temperature and relative humidity gradient). After 1 week of storage, the flavoured sponge cake headspace was SPME-extracted directly into the packaging and analysed by D-GC–O. The sponge cake global odour was better retained if plastic film rather than treated-papers was used, for both flavourings. Changes in th…
Three-Dimensional Microstructural Properties of Nanofibrillated Cellulose Films
2014
Abstract: Nanofibrillated cellulose (NFC) films have potential as oxygen barriers for, e.g., food packaging applications, but their use is limited by their hygroscopic characteristics. The three-dimensional microstructure of NFC films made of Pinus radiata (Radiata Pine) kraft pulp fibres has been assessed in this study, considering the structural development as a function of relative humidity (RH). The surface roughness, micro-porosity, thickness and their correlations were analyzed using X-ray microtomography (X–μCT) and computerized image analysis. The results are compared to those from scanning electron microscopy and laser profilometry. Based on a series of films having varying amounts…