Humidity influence on mechanics of paper materials: joint numerical and experimental study on fiber and fiber network scale

Paper materials are well-known to be hydrophilic unless chemical and mechanical processing treatments are undertaken. The relative humidity impacts the fiber elasticity, the interfiber joint behavior and the failure mechanism. In this work, we present a comprehensive experimental and computational study on mechanical properties of the fiber and the fiber network under humidity influence. The manually extracted cellulose fiber is exposed to different levels of humidity, and then mechanically characterized using atomic force microscopy, which delivers the humidity dependent longitudinal Young’s modulus. We describe the relation and calibrate the data into an exponential function, and the obtained relationship allows calculation of fiber elastic modulus at any humidity level. Moreover, by using confoncal laser scanning microscopy, the coefficient of hygroscopic expansion of the fibers is determined. We further present a finite element model to simulate the deformation and the failure of the fiber network. The model includes the fiber anisotropy and the hygroscopic expansion using the experimentally determined constants, and further considers interfiber behavior and debonding by using a humidity dependent cohesive zone interface model. Simulations on exemplary fiber network samples are performed to demonstrate the influence of different aspects including relative humidity and fiber-fiber bonding parameters on the mechanical features, such as force-elongation curve, strength and extensibility. Finally, we provide computational insights for interfiber bond damage pattern with respect to different humidity level as further outlook.

Boronic Ester-Polyurethane as a Self-Healing Coating Material for Offshore Top Side Structures Application

Polymer coatings, especially epoxy and polyurethane paint systems, have been widely used to prevent corrosion of metallic components and structures. However, due to environmental and mechanical effects, the barrier efficiency of the coatings may be substantially compromised during transportation and service, as demonstrated by localized scratches, delamination, or stress-related microcracks. Application of a self-healing coating that can restore damages and recover its performance with minimal external intervention could prevent corrosion at the damaged coating. In this present work, the healing efficiency and long-term durability of Boronic Ester (BE) blended with Polyurethane (PU) as a self-healing system for top side coating of offshore platform structures was investigated. The BE was mixed at a ratio of 50:50 with PU resin and applied as a top layer on a PU coated steel plate with a thickness of approximately 300-350 μm. The healing efficiency, mechanical performance, and durability under simulated environmental conditions such as salt spray and UV were investigated according to the related ASTM standards. As a first step, the electrical impedance spectroscopy (EIS) and 3D profilemeter microscope were used to assess the healing ability of the scratched coating at room temperature and humidity level of 85 %. The mechanical performance of the self-healing coating layer was evaluated using a pull off adhesion test to investigate the compatibility of the self-healing system with the existing commercial PU topcoat system, while a long term 3000 hours salt spray and 4200 hours cyclic UV test were performed to evaluate the self-healing coating's durability in harsh conditions. Preliminary assessment using EIS and 3D profilemeter microscopes on the scratched PU/BE self-healing coating revealed significant healing efficiency of more than 80% for healing condition at ambient temperature and humidity level of 85%. The self-healing coating layer also demonstrated excellent adhesion efficiency, with adhesion greater than 300 psi suggesting good compatibility of the BE-PU layer with commercial PU coating. The salt spray and cyclic UV tests that were performed to determine the durability of the self-healing coating revealed that the 50BE/50PU layer remained intact and exhibited good healing performance with more than 80% efficiency even after exposure to harsh conditions. The findings from the study demonstrated that the BE/PU material has the potential to be used as a self-healing system for topside coating of offshore platforms structures, thereby lowering maintenance costs.

The effects of temperature and exogenous auxin on cutting propagation of some junipers

From past to the present, cultural, medicinal, landscape and culinary use of junipers has contrib­uted to it being one of the most widely distributed woody plants in the world. Therefore, it is so important that finding appropriate production methods to obtain quality seedlings in line with the usage area. In the present study, it was tried to determine the best conditions and applications on propagation by cuttings of three juniper taxa including Juniperus communis L. ‘Hibernica’, Juniperus chinensis L. ‘Stricta’, and Juniperus chinensis L. ‘Stricta Variegata’. For this purpose, two different greenhouse treatments (Greenhouse-1 with the air temperature at 20±2°C, rooting table temperature at 25±2°C and humidity level at 70±2%; Green­house-2 with the air temperature at 20±2°C, rooting table temperature at 20±2°C and humidity level at 70±2%) and different auxin applications (Indole-3-Butyric Acid, Indole-3-Acetic Acid and α-Naphthalene Acetic Acid at concentrations of 3000 and 5000 ppm) were designed. The highest rooting percentages were generally achieved in Greenhouse-1. IAA 5000 ppm treatment for J. communis ‘Hibernica’ (93.33%) and J. chinensis ‘Stricta’ (66.67%, also in Greenhouse-2) and IBA 3000 ppm treatment for J. chinensis ‘Stricta Var­iegata’ (60.00%) showed the best rooting results. This study, in which the best production conditions are investigated in some juniper taxa, is a guiding feature for the producers to ensure the sustainable utilization of junipers.

A comparison of the effect of indoor thermal and humidity condition on young and older adults' comfort and skin condition in winter

Dry indoor air has been identified as the main cause of dry skin in winter which greatly affects older occupants' wellbeing, but HVAC design standards are based on average adults and do not specify a humidity level that can prevent dry skin. A field study was carried out to understand the difference between the younger and older people with regards to thermal and humidity comfort and skin condition in winter. The study proves a research procedure that is friendly to and preferred by the participants to measure the effect of the indoor environment on their comfort and skin condition in a real living environment setting. The results suggest that younger and older occupants are different in thermal comfort, specifically older occupants prefer a warmer environment than younger occupants, and the neutral temperature produced by the predicted mean vote method is not warm enough for older occupants. The study also suggests stratum corneum hydration appears to be a good indicator to present the effect of indoor humidity on the occupants' skin condition, which can be used to determine the minimum humidity level to reduce the risk of suffering dry skin in winter.

Carbon Dioxide Footprint and Its Impacts: A Case of Academic Buildings

Carbon emissions have been considered a major reason behind climate change and global warming. Various studies report that rapid urbanization and the changing demands of 21st century life have resulted in higher carbon emissions. This study aims to examine the carbon footprints in an academic building to observe the carbon dioxide (CO2) levels at crucial landmarks and offices. A sensor-based automated system was designed and implemented for the collection of CO2 concentrations at selected locations. In the final stage, a CO2 footprint map was generated to highlight the vulnerable areas of CO2 in the academic building. It was concluded that offices have higher CO2 concentrations at both intervals (morning and afternoon), followed by the laboratory, corridors, and praying area. The CO2 concentration did not exceed 500 ppm at any location. Thus, all locations other than offices had normal CO2 concentration levels. Similarly, the humidity level was also satisfactory. The average humidity level was below 50%, which is below the permissible value of 65%. The recommended range for temperature values as per ASHRAE standards is 22.5 °C to 25.5 °C, except for prayer places. It was concluded that the selected academic institute is providing a good environment to the users of the building, but that may change once the academic institute becomes fully functional after COVID-19. This study assists the stakeholders in making guidelines and necessary actions to reduce CO2 concentration in academic buildings, as it is expected to rise once the human load increases in the next academic year. The suggested approach can be used in any other country and the results will vary based on the building type, building energy type, and building ventilation design.

Effect of Relative Humidity on Mycelial Growth of Cercospora canescens

The relative humidity studies revealed that maximum mycelial of fungus was observed at 90 per cent relative humidity (89.00 mm), which was followed by 100 per cent (86.30 mm). The least mycelia growth was observed at 50 per cent (45.30 mm). A significant decrease in mycelium growth was observed at 80, 70 and 60 per cent (80.40 mm, 70.20 mm and 57.00 mm) humidity level, respectively. Each fungus has its relative humidity range for the growth.

Some Characteristics Of Transpiration Of Promising Soybean’s Varieties

The article presents data obtained from the study of the daily intensity of transpiration during the flowering stage of soybean varieties. According to the data on the diurnal variation of transpiration intensity, this process was accelerated in Vilana and Ustoz MM-60 varieties of soybeans, and a relative decrease in intensity was observed in Baraka and Tomaris man-60 varieties. Different variations in the intensity of transpiration in the cross section of the studied varieties may depend on the biological characteristics of the varieties as well as the air temperature and its relative humidity level.

Cocoa (Theobroma cacao L.) harvest and postharvest in Tabasco, Mexico

Objective: To characterize the harvest and postharvest of the cocoa managementsystem at La Chontalpa, Tabasco, Mexico.Design / methodology / approach: The study took place in the towns ofFrancisco Trujillo Gurría and Ernesto Aguirre Colorado de Huimanguillo, Tabasco,Mexico. The study was descriptive and accounted for 51 producers and thoseresponsible for the cocoa profit centers. Producers were chosen through targetedsampling. A survey on their harvest and postharvest was applied, in addition todirect assessment in plantations and profit centers.Results: The cocoa harvesting is manual. The producers cut the ripe and almostripe fruits, do not store and 58.8% of them do not break the fruit. With a “machete”cut the fruit in half and manually extract the grains. The fresh grains are sold at aprofit. The cocoa is then fermented in wooden boxes, dried artificially, natural, or ina combined way, and packed in “yute” bags for sale. Profit centers do not keeptrack of their grain origin and make no selection or determine product quality. Study limitations / implications: All producers harvest in the same way, but theprocesses during post-harvest could differ at different collection centers.Findings / conclusions: The harvest of cocoa fruits at different maturity and thelack of storage causes a heterogeneous fermentation. The humidity level duringthe drying process is empirically determined.

Capacitance and Resistivity Measurements of Polythiophene /Metallic Nanoparticles-based Humidity Sensors

Capacitive–resistive humidity sensors based on polythiophene (P3HT) organic semiconductor as an active material hybrid with three types of metallic nanoparticles (NP) (Ag, Al, and Cu) were synthesized by pulsed laser ablation (PLA). The hybrid P3HT/metallic nanoparticles were deposited on indium-tin-oxide (ITO) substrate at room temperature. The surface morphology of theses samples was studied by using field emission scanning electron micrographs (FE-SEM), which indicated the formation of nanoparticles with grain size of about 50nm. The electrical characteristics of the sensors were examined as a function of the relative humidity levels. The sensors showed an increase in the capacitance with variation in the humidity level. While the resistivity While the resistivity decrease nonlinearity in the variation of humidity level from 10% to 100%.. The results show that the recovery and response times were higher for the Al/P3HT/Cu/Al sensor compared with those of the other nanoparticles.