scholarly journals Magnesium oxychloride boards: understanding a novel building material

2020 ◽  
Vol 53 (5) ◽  
Author(s):  
Timothy A. Aiken ◽  
Mark Russell ◽  
Daniel McPolin ◽  
Leo Bagnall
Keyword(s):  
Relative Humidity ◽  
Magnesium Oxide ◽  
Fire Resistance ◽  
Building Material ◽  
Ease Of Use ◽  
Precise Nature ◽  
Magnesium Oxychloride ◽  
Fibre Cement ◽  
The Difference ◽  
Cement Board

Abstract Magnesium oxide type building boards are a relatively new alternative to traditional sheeting materials such as plywood, gypsum plasterboard and fibre-cement board. They have many advantages; strength, lightweight, ease of use and excellent fire resistance, which has become increasingly important as demanded by industry and required by more stringent legislation. Recently cases of durability issues associated with magnesium oxychloride boards in Denmark have emerged, however the precise nature of the problem was not established. These issues have been related to magnesium oxychloride boards which were exposed to high levels of moisture. In this paper the mechanism of the failures observed in Denmark has been investigated. The difference in quality between various magnesium oxychloride boards available in the market was also studied. It was found that there are significant differences, both physically and chemically, between magnesium oxychloride boards supplied from different manufacturers. Crucially, the performance of each board when exposed to high levels of relative humidity was vastly different. Some of the boards investigated displayed behaviour similar to that observed in Denmark, whilst other boards exhibited substantial resistance to humid environments and had not deteriorated after 60 weeks of exposure.

Improved Magnesium Cement for Durable Hemp Composite Boards

2022 ◽  
Author(s):  
Jelizaveta Zorica ◽  
Maris Sinka ◽  
Genadijs Sahmenko ◽  
Diana Bajare
Keyword(s):  
Compressive Strength ◽  
Water Resistance ◽  
Chemical Reactivity ◽  
Ease Of Use ◽  
Lower Amount ◽  
Insulation Material ◽  
Magnesium Oxychloride ◽  
Magnesium Oxychloride Cement ◽  
Cement Board ◽  
Oxychloride Cement

Hemp concrete is a well-known bio-based building material, but due to its relatively low compressive strength is mainly used as an insulation material with a load-bearing wooden frame. There are possibilities to expand hemp concrete application in construction by substituting traditional lime with magnesium cement. Magnesium oxychloride cement is a material already known for some time and nowadays used in building board production. Strength, lightweight, ease of use are advantages that highlight relatively new magnesium oxychloride type boards compared to traditional sheeting materials such as plywood, gypsum plasterboard and fibre-cement board. Therefore, similar parameters are thought to be reached by producing magnesium oxychloride hemp board. In this work, magnesium cement water resistance was studied and possibilities to improve it was examined by adding fly ash and nanosilica. Among the nanomaterials used in building materials, nanosilica has gained significant interest by performing a beneficial effect in improving the mechanical properties of concretes. In addition, due to its ultrafine size and high chemical reactivity, the performance of nanosilica is much better with a lower amount of admixture required. Results show that applied nanosilica slightly reduced the compressive strength of magnesium cement in a dry state, but at the same time significantly increased its water resistance. Hemp magnesium oxychloride cement board prototype samples were produced and demonstrate promising results for further manufacturing of hemp composite boards.

scholarly journals Investigation of monthly variations in the efficiencies of photovoltaics due to sunrise and sunset times

2020 ◽  
Vol 18 (1) ◽  
pp. 310
Author(s):  
Armstrong O. Njok ◽  
Julie C. Ogbulezie ◽  
Manoj Kumar Panjwani ◽  
Raja Masood Larik
Keyword(s):  
Relative Humidity ◽  
Solar Energy ◽  
Electrical Energy ◽  
Time Of Day ◽  
Peak Efficiency ◽  
Pv Module ◽  
Average Relative Humidity ◽  
The Difference ◽  
Monthly Variations ◽  
Different Levels

<p>The effect of time of day and month on the efficient conversion of solar energy to electrical energy using a polycrystalline (PV) module in calabar was studied. A KT-908 precision digital hygrometer and thermometer, and a M890C+ digital multimeter were used in the process. Results obtained shows that photovoltaic produce different levels of peak efficiencies at different times of the day for different months due to the difference in sunrise and sunset times for the months. The results also indicated that photovoltaics will be more efficient in months with low average relative humidity couple with low panel temperature. A peak efficiency of 77% at 12:30 in the month of April was observed before dropping to 73% at 12:00 in the month of May, indicating that there might be further drop in efficiency as we proceed further into the year. Results also show that photovoltaics are more efficient before noon in the month of May than in April while the reverse will be observed in the afternoon. </p>

scholarly journals Electronic Ticketing System and Traveler Purchasing Intention

2013 ◽  
Vol 217 ◽  
pp. 129-146
Author(s):  
THẢO HOÀNG THỊ PHƯƠNG
Keyword(s):  
Regression Models ◽  
Online Shopping ◽  
Behavioral Control ◽  
Ease Of Use ◽  
Perceived Behavioral Control ◽  
Perceived Ease Of Use ◽  
Demographic Groups ◽  
Purchasing Intention ◽  
Shopping Experience ◽  
The Difference

This research aims to identify the importance of factors that influence customer intention of purchasing electronic air ticket (e-ticket). The research compares the difference in purchasing intentions based on e-ticketing between demographic groups of age, income, educational level, and online shopping experience. With the sample size of 295 travelers, the regression models and ANOVA tests are used to process and explain data. The research detects four components, namely, perceived system usefulness, perceived ease of use, perceived behavioral control, and security of transaction that influence the consumer intention to buy e-ticket. The paper then recommends managerial solutions to the development of an electronic ticketing system in particular and e-commerce in general.

Axial Compression Behaviour Analysis of Insulated Concrete Form (ICF) Wall Panel with Fibre Cement Board

2022 ◽  
Vol 1048 ◽  
pp. 387-395
Author(s):  
Joel Joseph Shelton ◽  
Mohammad Izazs ◽  
C. Daniel ◽  
A. Arun Solomon
Keyword(s):  
Axial Compression ◽  
Testing Machine ◽  
Peak Load ◽  
Compressive Loading ◽  
Wall Panel ◽  
Maximum Displacement ◽  
Concrete Form ◽  
Wall Panels ◽  
Fibre Cement ◽  
Cement Board

Nowadays, one of the fastest growing technique is an Insulated Concrete Form (ICF). It has advantages like cost-effective, less maintenance, soundproof, energy-efficient, waterproof and disaster-resistant. ICF wall panels are made by interlocking Fibre Cement Board (FCB) sheet which poured in placed concrete. In this study, the behaviour of the ICF wall panel under axial compression is examined with experimental and analytical methods. ICF wall panels cast with various thickness and dense FCB are tested under axial compression. ICF panels with 1.2gm3/cm dense FCB with changing width of 6mm and 10mm were casted for experimental analysis. The experiments were carried out in an universal testing machine with the capacity of 600 kN. The maximum peak load of 540 kN is observed in FCB of 10mm thick and the maximum displacement of 13mm is observed in FCB80 at the peak load. An analytical investigation is carried with Euler’s crippling load equation and an average variation of 12% is observed between analytical and experimental results. It is concluded that the ICF system of construction provides desirable plastic behaviour against axial compressive loading. Hence ICF is recommended for construction to get the maximum benefits of the wall while it reaches ultimate strain.

Mid-Holocene drylands: A multi-model analysis using Paleoclimate Modelling Intercomparison Project Phase III (PMIP3) simulations

The Holocene ◽  
2019 ◽  
Vol 29 (9) ◽  
pp. 1425-1438
Author(s):  
Shanshan Liu ◽  
Dabang Jiang ◽  
Xianmei Lang
Keyword(s):  
Relative Humidity ◽  
Potential Evapotranspiration ◽  
Aridity Index ◽  
Phase Iii ◽  
Collective Effects ◽  
Model Data ◽  
Intercomparison Project ◽  
The Difference ◽  
Paleoclimate Modelling Intercomparison Project ◽  
Paleoclimate Modelling

This study examines changes in aridity levels during the mid-Holocene (approximately 6000 cal. yr ago) using multi-model simulations from the Paleoclimate Modelling Intercomparison Project Phase III. Overall, there is little difference in the total area of drylands from the preindustrial period; global drylands are 8% wetter than during the preindustrial period as measured by an aridity index; and 16% of preindustrial drylands convert to a wetter climate subtype, double the sum of zones that are replaced by a drier category. Considerable variations are present among regions with major contractions of each dryland subtype from northern Africa to South Asia and the main expansions of arid, semiarid, and dry subhumid climates in southern hemisphere continents. The difference in precipitation is the leading factor of the aforementioned changes. The second factor is the altered potential evapotranspiration as mainly induced by relative humidity, which contributes to additional aridity changes in a same direction as precipitation does. The collective effects of precipitation and relative humidity account for more than 80% of the dryland variations. In comparison, the simulated aridity change is in reasonable agreement with reconstructions, while there are model–data discrepancies for Australia and uncertainties across proxies for southern Africa.

Thermal Performance Comparison between Single and Double Storey Terrace Houses in Melaka, Malaysia

2016 ◽  
Vol 835 ◽  
pp. 416-422
Author(s):  
Fahanim Abdul Rashid ◽  
Asrul Mahjuddin Ressang Aminuddin ◽  
Norafida Ab. Ghaffar
Keyword(s):  
Relative Humidity ◽  
Thermal Comfort ◽  
Case Studies ◽  
Thermal Performance ◽  
High Energy ◽  
Performance Comparison ◽  
Building Envelope ◽  
The Difference ◽  
Economic Developments ◽  
Housing Typology

Over the past decade many studies were conducted to investigate the thermal performance of terraced houses in Malaysia. It was found that this housing typology failed to address the need for thermal comfort and alternatives to the narrow frontage with deep plan have been proposed with simulated good thermal performance. Although this is good progress for new generation of terraced houses, millions of units of terraced houses are still in use and new units with the outdated existing plans continued to get built due to consistently very high demand due to progressive urbanisation and rapid economic developments. Therefore, it is imperative that the thermal comfort issue for existing terraced houses is dealt with and through this paper a comparison between single and double storey terraced houses is made through analysis of indoor environmental monitoring (ambient temperature, relative humidity and air velocity) of two (2) selected case studies in Merlimau, Melaka. Contrary to popular belief, it is found that there is no statistical difference between both sets of indoor temperature and relative humidity between the case studies. This finding is indicative of the consistent and stable temporal temperature highs and lows in a 24 hour cycle despite the difference in indoor volume and distance between the ground floor and the roof cavity. Much of the reason is due to the materiality of the terraced houses construction and unsealed and uninsulated building envelope. Therefore, further research into improving the thermal performance of existing terraced houses of any typology have to be conducted to allow thermal comfort and to reduce reliance on high energy consuming air-conditioning.

scholarly journals Influence of Below-Cloud Evaporation on Deuterium Excess in Precipitation of Arid Central Asia and Its Meteorological Controls

2016 ◽  
Vol 17 (7) ◽  
pp. 1973-1984 ◽  
Author(s):  
Shengjie Wang ◽  
Mingjun Zhang ◽  
Yanjun Che ◽  
Xiaofan Zhu ◽  
Xuemei Liu
Keyword(s):  
Relative Humidity ◽  
Central Asia ◽  
Air Temperature ◽  
Sampling Site ◽  
Heavy Precipitation ◽  
Cloud Base ◽  
Deuterium Excess ◽  
Arid Central Asia ◽  
Observation Network ◽  
The Difference

Abstract The deuterium excess is a second-order parameter linking water-stable oxygen and hydrogen isotopes and has been widely used in hydrological studies. The deuterium excess in precipitation is greatly influenced by below-cloud evaporation through unsaturated air, especially in an arid climate. Based on an observation network of isotopes in precipitation of arid central Asia, the difference in deuterium excess from cloud base to ground was calculated for each sampling site. The difference on the southern slope of the Tian Shan is generally larger than that on the northern slope, and the difference during the summer months is greater than that during the winter months. Generally, an increase of 1% in evaporation of raindrops causes deuterium excess to decrease by approximately 1‰. Under conditions of low air temperature, high relative humidity, heavy precipitation, and large raindrop diameter, a good linear correlation is exhibited between evaporation proportion and difference in deuterium excess, and a linear regression slope of &lt;1‰ %−1 can be seen; in contrast, under conditions of high air temperature, low relative humidity, light precipitation, and small raindrop diameter, the linear relationship is relatively weak, and the slope is much larger than 1‰ %−1. A sensitivity analysis under different climate scenarios indicates that, if air temperature has increased by 5°C, deuterium excess difference decreases by 0.3‰–4.0‰ for each site; if relative humidity increases by 10%, deuterium excess difference increases by 1.1‰–10.3‰.

Behaviour of Pigeon Excreta on Masonry Surfaces

2018 ◽  
Vol 23 (1) ◽  
pp. 15-28 ◽  
Author(s):  
Dirk HR Spennemann ◽  
Melissa Pike ◽  
Maggie J Watson
Keyword(s):  
Relative Humidity ◽  
Environmental Conditions ◽  
Building Material ◽  
Urban Areas ◽  
Real Life ◽  
The Body ◽  
Individual Bird ◽  
Bird Droppings ◽  
Pigeon Droppings ◽  
The Impact

Abstract Pigeon droppings are implicated in spoiling and decay of buildings. Several studies have examined the effects and chemistry of accumulations of pigeon droppings under highly localised pigeon roosts. Scant information exists on the impact caused by individual pigeon droppings at perch sites, even though these constitute the majority of bird use in urban areas. This study experimentally examined the processes that affect masonry immediately after pigeon excreta have been voided from the body and what effects discrete, fresh pigeon droppings have on different kinds of sandstone. The experiments demonstrated the susceptibility of freshly deposited excreta to environmental conditions (relative humidity and precipitation). In real-life situations, with pigeon excreta deposited on window ledges, cornices and parapets, the majority of damage would occur within the first two weeks of deposition. After that, the majority of individual droppings would have either dissolved or desiccated to such a degree that they would have rolled off. Much of the observed staining is superficial. While individual bird droppings make a building look dirty, even for months at a time, the effect on the building material is not substantial unless other factors come into play such as colonisation of the excreta by mould or leaching of salts from the excreta.

scholarly journals Theoretical analysis of mixing in liquid clouds – Part IV: DSD evolution and mixing diagrams

2018 ◽  
Vol 18 (5) ◽  
pp. 3659-3676 ◽  
Author(s):  
Mark Pinsky ◽  
Alexander Khain
Keyword(s):  
Relative Humidity ◽  
Droplet Size Distribution ◽  
Droplet Evaporation ◽  
Cloud Fraction ◽  
Time Dependent ◽  
Droplet Concentration ◽  
The Mean ◽  
The Difference ◽  
Mixing Diagrams ◽  
Dependent Processes

Abstract. Evolution of droplet size distribution (DSD) due to mixing between cloudy and dry volumes is investigated for different values of the cloud fraction and for different initial DSD shapes. The analysis is performed using a diffusion–evaporation model which describes time-dependent processes of turbulent diffusion and droplet evaporation within a mixing volume. Time evolution of the DSD characteristics such as droplet concentration, LWC and mean volume radii is analyzed. The mixing diagrams are plotted for the final mixing stages. It is shown that the difference between the mixing diagrams for homogeneous and inhomogeneous mixing is insignificant and decreases with an increase in the DSD width. The dependencies of the normalized cube of the mean volume radius on the cloud fraction were compared with those on normalized droplet concentration and found to be quite different. If the normalized droplet concentration is used, mixing diagrams do not show any significant dependence on relative humidity in the dry volume. The main conclusion of the study is that traditional mixing diagrams cannot serve as a reliable tool for analysis of mixing type.

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